Derivatives and Hedging (Tables)

12 Months Ended

Mar. 31, 2017

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Derivative Assets at Fair Value [Table Text Block]

								Gross amounts not offset in the Balance Sheet
	Gross amounts of recognized assets		Gross amounts offset in the Balance Sheet			Net amount of derivative assets presented in the Balance Sheet		Financial instruments		Cash collateral		Net amount as of March 31, 2016
Derivative instruments designated as hedging instruments (See Note 6)
Interest rate swap	$	—	$	—		$	—	$	7,599	$	—	$	7,599
Derivative instruments not designated as hedging instruments
Currency forward contracts	1,933		(963		)	970		—		—		970
Futures contracts relating to seed capital investments	—		—			—		81		1,840		1,921
Total derivative instruments not designated as hedging instruments	1,933		(963		)	970		81		1,840		2,891
Total derivative instruments	$	1,933	$	(963	)	$	970	$	7,680	$	1,840	$	10,490

								Gross amounts not offset in the Balance Sheet
	Gross amounts of recognized assets		Gross amounts offset in the Balance Sheet			Net amount of derivative assets presented in the Balance Sheet		Financial instruments		Cash collateral		Net amount as of March 31, 2017
Derivative instruments not designated as hedging instruments
Currency forward contracts	$	3,470	$	(928	)	$	2,542	$	—	$	—	$	2,542
Futures contracts relating to seed capital investments	—		—			—		176		2,878		3,054
Total derivative instruments not designated as hedging instruments	$	3,470	$	(928	)	$	2,542	$	176	$	2,878	$	5,596

Schedule of Derivative Liabilities at Fair Value [Table Text Block]

									Gross amounts not offset in the Balance Sheet
	Gross amounts of recognized liabilities			Gross amounts offset in the Balance Sheet		Net amount of derivative liabilities presented in the Balance Sheet			Financial instruments			Cash collateral		Net amount as of March 31, 2017
Derivative instruments not designated as hedging instruments
Currency forward contracts	$	(3,641	)	$	751	$	(2,890	)	$	—		$	—	$	(2,890	)
Futures contracts relating to seed capital investments	—			—		—			(1,632		)	4,155		2,523
Total derivative instruments not designated as hedging instruments	$	(3,641	)	$	751	$	(2,890	)	$	(1,632	)	$	4,155	$	(367	)

									Gross amounts not offset in the Balance Sheet
	Gross amounts of recognized liabilities			Gross amounts offset in the Balance Sheet		Net amount of derivative liabilities presented in the Balance Sheet			Financial instruments			Cash collateral		Net amount as of March 31, 2016
Derivative instruments not designated as hedging instruments
Currency forward contracts	$	(16,364	)	$	280	$	(16,084	)	$	—		$	—	$	(16,084	)
Futures contracts relating to seed capital investments	—			—		—			(1,995		)	5,920		3,925
Total derivative instruments not designated as hedging instruments	$	(16,364	)	$	280	$	(16,084	)	$	(1,995	)	$	5,920	$	(12,159	)

Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance

		Years Ended March 31,
		2017					2016					2015
	Income Statement Classification	Gains		Losses			Gains		Losses			Gains		Losses
Derivatives not designated as hedging instruments
Currency forward contracts for:
Operating activities	Other expense	$	14,524	$	(13,098	)	$	7,887	$	(19,547	)	$	5,150	$	(16,518	)
Seed capital investments	Other non-operating income (expense)	2,681		(2,443		)	547		(1,611		)	2,491		(259		)
Other non-operating activities(1)	Other non-operating income (expense)	—		—			—		(4,493		)	—		—
Futures and forward contracts for seed capital investments	Other non-operating income (expense)	2,103		(18,602		)	11,270		(9,206		)	10,801		(15,413		)
Total gain (loss) from derivatives not designated as hedging instruments		19,308		(34,143		)	19,704		(34,857		)	18,442		(32,190		)
Derivative designated as a fair value hedge (See Note 6)
Interest rate swap	Interest expense	—		—			5,710		—			5,462		—
Reverse treasury rate lock	Other non-operating income (expense)	—		—			—		—			638		—
Derivative designated as a cash flow hedge (See Note 6)
Interest rate swap (termination)	Other non-operating income (expense)	—		(3,662		)	—		—			—		—
Interest rate swap	Interest expense	—		(764		)	—		—			—		—
Total		$	19,308	$	(38,569	)	$	25,414	$	(34,857	)	$	24,542	$	(32,190	)

(1) Relates to a currency forward executed in August 2015 and closed in October 2015 in connection with the October 2015 acquisition of RARE Infrastructure.