Commitments and Contingencies Information Regarding Rental Commitments (Details 2) - USD ($) $ in Thousands		12 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Property Subject to or Available for Operating Lease [Line Items]
Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals		$ 126,280
Percentage of Sublease Rentals due from Counterparty		35.00%
Operating Leases, Future Minimum Payments Due	[1]	$ 677,976
Commitments Related to Vacated and Subleased Space [Member]
Property Subject to or Available for Operating Lease [Line Items]
Valuation Allowances and Reserves, Balance		28,821	$ 31,745
Commitments Related to Vacated Space that Remains Vacant [Member]
Property Subject to or Available for Operating Lease [Line Items]
Valuation Allowances and Reserves, Balance		10,867	20,495
Operating Leases, Future Minimum Payments Due		20,443
Vacated Office Space [Member]
Property Subject to or Available for Operating Lease [Line Items]
Valuation Allowances and Reserves, Balance		39,688	52,240	$ 45,939
Valuation Allowances and Reserves, Period Increase (Decrease)		(2,700)	$ 7,200
EnTrustPermal [Member] | Vacated Office Space [Member]
Property Subject to or Available for Operating Lease [Line Items]
Valuation Allowances and Reserves, Period Increase (Decrease)		$ (4,495)

[1] (1) Includes $615,651 in real estate and equipment leases and $62,325 in service and maintenance agreements.