Long-Term Debt Interest Rate Swap (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2015	Jun. 23, 2014
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Gain on Derivative	$ 12,012	$ 11,486	$ 15,704	$ 18,231
Debt Instrument, Fair Value Disclosure	(4,108)		(4,108)
Interest Rate Swap [Member] | Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount						$ 250,000
Derivative Instruments in Hedges, Assets, at Fair Value	4,108		4,108		$ 5,462
Other Income [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(3,151)	(4,145)		(3,596)
Other Expense [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(3,151)		(1,354)	3,596
Interest Expense [Member] | Interest Rate Swap [Member] | Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Change in Unrealized Gain (Loss)			(1,354)
Derivative, Gain on Derivative	0	$ 4,145	620	$ 3,596
2.7% Senior Notes [Member] | Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Debt Instrument, Fair Value Disclosure	$ (4,108)		$ (4,108)		$ (5,462)