| 
                                Mar 2019
                             | 
                            
                                
                                    The Wellington Trust Company, National Association
                                
                             | 
                            
                                1,914,661
                             | 
                            
                            
                                2.53%
                             | 
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                        
                    
                        
                            
                                
                                    | 
                                     | 
                                    
                                        
                                         | 
                                    
                                    
                                        
                                         | 
                                    
                                
                                
                        
                        
                            | 
                                Dec 2018
                             | 
                            
                                
                                    The Wellington Trust Company, National Association
                                
                             | 
                            
                                2,330,268
                             | 
                            
                            
                                3.08%
                             | 
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                        
                    
                        
                            
                                
                                    | 
                                     | 
                                    
                                        
                                         | 
                                    
                                    
                                        
                                         | 
                                    
                                
                                
                        
                        
                            | 
                                Sep 2018
                             | 
                            
                                
                                    The Wellington Trust Company, National Associationmultiple Collective Investment Funds Trust, Opport
                                
                             | 
                            
                                2,335,664
                             | 
                            
                            
                                3.09%
                             | 
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                        
                    
                        
                            
                                
                                    | 
                                     | 
                                    
                                        
                                         | 
                                    
                                    
                                        
                                         | 
                                    
                                
                                
                        
                        
                            | 
                                Jun 2018
                             | 
                            
                                
                                    The Wellington Trust Company, National Associationmultiple Collective Investment Funds Trust, Opport
                                
                             | 
                            
                                1,465,223
                             | 
                            
                            
                                1.94%
                             | 
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                        
                    
                        
                            
                                
                                    | 
                                     | 
                                    
                                        
                                         | 
                                    
                                    
                                        
                                         | 
                                    
                                
                                
                        
                        
                            | 
                                Mar 2018
                             | 
                            
                                
                                    The Wellington Trust Company National Associationmultiple Collective Investment Funds Trust Opportun
                                
                             | 
                            
                                1,453,893
                             | 
                            
                            
                                1.92%
                             | 
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                        
                    
                        
                            
                                
                                    | 
                                     | 
                                    
                                        
                                         | 
                                    
                                    
                                        
                                         | 
                                    
                                
                                
                        
                        
                            | 
                                Dec 2017
                             | 
                            
                                
                                    The Wellington Trust Company National Associationmultiple Collective Investment Funds Trust Opportun
                                
                             | 
                            
                                1,477,303
                             | 
                            
                            
                                1.95%
                             | 
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                        
                    
                        
                            
                                
                                    | 
                                     | 
                                    
                                        
                                         | 
                                    
                                    
                                        
                                         | 
                                    
                                
                                
                        
                        
                            | 
                                Sep 2017
                             | 
                            
                                
                                    The Wellington Trust Co
                                
                             | 
                            
                                1,483,273
                             | 
                            
                            
                                1.96%
                             | 
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                        
                    
                        
                            
                                
                                    | 
                                     | 
                                    
                                        
                                         | 
                                    
                                    
                                        
                                         | 
                                    
                                
                                
                        
                        
                            | 
                                Jun 2017
                             | 
                            
                                
                                    The Wellington Trust Company Nataional Assiciationmultiple Collective Investment Funds Trust - Oppor
                                
                             | 
                            
                                1,242,086
                             | 
                            
                            
                                1.64%
                             | 
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 | 
                            
                            
                                
                                    0
                                 | 
                                
                                    0.00%
                                 |