Summary Of Major Accounting Policies - Principles of Consolidation And Repurchases (Details)	Mar. 31, 2018
Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Percentage	50.00%
Equity Method Investment, Ownership Interest Threshold For Consolidation, Percentage	20.00%
Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Interest Threshold For Consolidation, Percentage	50.00%