Consolidated Company-Sponsored Investment Funds (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Derivative [Line Items]
Gain (loss) on derivative instruments	$ (5,387,000)	$ (5,052,000)	$ (14,879,000)	$ (8,609,000)
Cash collateral payable to trade counterparties	0		0		$ 800,000
Cash collateral received	5,600,000		5,600,000		6,200,000
Net assets of investment products that are non-consolidated VIEs	49,400,000,000		49,400,000,000
Maximum risk of loss in investment in VIEs	19,500,000		19,500,000
VIEs
Derivative [Line Items]
Futures, forwards and swaps held	11,600,000		11,600,000		2,900,000
Asset Derivatives	12,900,000		12,900,000		3,200,000
Gain (loss) on derivative instruments	7,800,000	$ (300,000)	15,000,000	$ 2,700,000
Cash collateral payable to trade counterparties	88,000		88,000		461,000
Cash collateral received	3,800,000		3,800,000		$ 3,300,000
VOEs
Derivative [Line Items]
Cash collateral payable to trade counterparties	$ 0		$ 0