Consolidated Company-Sponsored Investment Funds - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Cash collateral payable to trade counterparties	$ 4,800,000	$ 500,000
Cash collateral received	4,500,000	8,800,000
Net assets of investment products that are non-consolidated VIEs	44,300,000,000
Maximum risk of loss in investment in VIEs	5,700,000
VIEs
Derivative [Line Items]
Futures, forwards and swaps held	500,000	8,400,000
Gains (losses) on derivatives	1,500,000	21,500,000
Cash collateral payable to trade counterparties	856,000	194,000
Cash collateral received	800,000	2,900,000
VOEs
Derivative [Line Items]
Futures, forwards and swaps held	14,000	300,000
Gains (losses) on derivatives	1,900,000	(400,000)
Cash collateral payable to trade counterparties	225,000	37,000
Cash collateral received	500,000	$ 200,000
Seed capital
Derivative [Line Items]
Seed investment in deconsolidated fund	$ 42,500,000