Consolidated Company-Sponsored Investment Funds (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Derivative [Line Items]
Gains (losses) on derivative instruments	$ (19,765,000)	$ 2,367,000
Cash collateral payable to trade counterparties	1,100,000		$ 4,800,000
Cash collateral received	3,700,000		4,500,000
Net assets of investment products that are non-consolidated VIEs	53,500,000,000
Maximum risk of loss in investment in VIEs	6,400,000
VIEs
Derivative [Line Items]
Futures, forwards and swaps held	200,000		500,000
Gains (losses) on derivative instruments	(1,100,000)	(14,900,000)
Cash collateral payable to trade counterparties	958,000		856,000
Cash collateral received	2,100,000		800,000
VOEs
Derivative [Line Items]
Futures, forwards and swaps held	400,000		14,000
Gains (losses) on derivative instruments	100,000	$ (500,000)
Cash collateral payable to trade counterparties	241,000		225,000
Cash collateral received	$ 900,000		$ 500,000