Derivatives and Hedging Gains and (Losses) of Derivative Instruments (Details) - Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member] - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain	$ 6,400	$ 3,416
Derivative Instruments Not Designated as Hedging Instruments, Loss	(4,423)	(5,948)
Derivative, Gain on Derivative	6,400	4,163
Derivative, Loss on Derivative	(5,398)	(5,948)
Forward Contracts [Member] | Other Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain	4,842	2,841
Derivative Instruments Not Designated as Hedging Instruments, Loss	(1,137)	(417)
Forward Contracts [Member] | Other Nonoperating Income (Expense) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain	28	33
Derivative Instruments Not Designated as Hedging Instruments, Loss	(595)	(354)
Future [Member] | Other Nonoperating Income (Expense) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain	1,530	542
Derivative Instruments Not Designated as Hedging Instruments, Loss	(2,691)	(5,177)
Interest Rate Swap [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain on Derivative	0	747
Derivative, Loss on Derivative	$ (975)	$ 0