Consolidated Company-Sponsored Investment Funds (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Derivative [Line Items]
Gain (loss) on derivative instruments	$ (4,891,000)	$ (8,042,000)	$ (19,770,000)	$ (16,651,000)
Cash collateral payable to trade counterparties	0		0		$ 800,000
Cash collateral received	6,400,000		6,400,000		6,200,000
Net assets of investment products that are non-consolidated VIEs	52,100,000,000		52,100,000,000
Maximum risk of loss in investment in VIEs	7,400,000		7,400,000
VIEs
Derivative [Line Items]
Futures, forwards and swaps held	14,100,000		14,100,000		2,900,000
Asset Derivatives	15,000,000		15,000,000		3,200,000
Gain (loss) on derivative instruments	3,800,000	$ (2,000,000)	18,800,000	$ 700,000
Cash collateral payable to trade counterparties	186,000		186,000		461,000
Cash collateral received	4,600,000		4,600,000		$ 3,300,000
VOEs
Derivative [Line Items]
Cash collateral payable to trade counterparties	$ 12,000		$ 12,000