Derivatives and Hedging (Tables)

9 Months Ended

Dec. 31, 2017

Derivative Instruments and Hedging Activities Disclosures [Line Items]

Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]

Transaction Date	Expiration Date	Aggregate Counterparty Initial Investment in ETF		Floating Rate	Aggregate Notional Amount as of December 31, 2017
October 10, 2017	April 2018	$	5,290	Three-month LIBOR plus 1.6%	$	5,314
July 26, 2017	July 2018	23,096		Three-month LIBOR plus 1.6%	23,584
June 6, 2017	June 2018	20,253		Three-month LIBOR plus 1.35%	22,168
		$	48,639		$	51,066

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, 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

								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 December 31, 2017
Derivative instruments not designated as hedging instruments
Currency forward contracts	$	7,617	$	(1,884	)	$	5,733	$	—	$	—	$	5,733
Total return swaps	—		—			—		1,450		3,003		4,453
Total derivative instruments not designated as hedging instruments	$	7,617	$	(1,884	)	$	5,733	$	1,450	$	3,003	$	10,186

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 December 31, 2017
Derivative instruments not designated as hedging instruments
Currency forward contracts	$	(360	)	$	191	$	(169	)	$	—		$	—	$	(169	)
Futures contracts relating to:
Seed capital investments	—			—		—			(1,633		)	6,356		4,723
Total return swaps	—			—		—			(410		)	2,380		1,970
Total futures contracts	—			—		—			(2,043		)	8,736		6,693
Total return swaps	—			—		—			(76		)	1,769		1,693
Total derivative instruments not designated as hedging instruments	$	(360	)	$	191	$	(169	)	$	(2,119	)	$	10,505	$	8,217

									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	)

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

		Three Months Ended December 31,
		2017					2016
	Income Statement Classification	Gains		Losses			Gains		Losses
Derivatives not designated as hedging instruments
Currency forward contracts relating to:
Operating activities	Other expense	$	2,005	$	(1,146	)	$	1,368	$	(6,199	)
Seed capital investments	Other non-operating income (expense)	624		(518		)	1,932		(837		)
Futures contracts relating to:
Seed capital investments	Other non-operating income (expense)	33		(6,864		)	1,965		(3,514		)
Total return swaps	Other non-operating income (expense)	—		(3,478		)	—		—
Total return swaps	Other non-operating income (expense)	1,796		(11		)	—		—
Total gain (loss) from derivatives not designated as hedging instruments		$	4,458	$	(12,017	)	$	5,265	$	(10,550	)

		Nine Months Ended December 31,
		2017					2016
	Income Statement Classification	Gains		Losses			Gains		Losses
Derivatives not designated as hedging instruments
Currency forward contracts relating to:
Operating activities	Other expense	$	10,980	$	(4,917	)	$	11,148	$	(13,085	)
Seed capital investments	Other non-operating income (expense)	251		(1,868		)	2,943		(1,752		)
Futures contracts relating to:
Seed capital investments	Other non-operating income (expense)	72		(18,082		)	2,676		(11,184		)
Total return swaps	Other non-operating income (expense)	89		(5,274		)	—		—
Total return swap	Other non-operating income (expense)	2,562		—			—		—
Total gain (loss) from derivatives not designated as hedging instruments		13,954		(30,141		)	16,767		(26,021		)
Derivative designated as a cash flow hedge (See Note 7)
Interest rate swap (termination)	Other non-operating income (expense)	—		—			—		(3,662		)
Interest rate swap	Interest expense	—		—			—		(764		)
Total		$	13,954	$	(30,141	)	$	16,767	$	(30,447	)