Consolidated Company-Sponsored Investment Funds - Offsetting of Derivative Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Derivative Asset [Abstract]
Cash Collateral Received	$ (4,800)	$ (500)
VIEs
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	3,410	30,636
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Assets Presented in the Statement of Financial Condition	3,410	30,636
Financial Instruments	0	0
Cash Collateral Received	(856)	(194)
Net Amount	2,554	30,442
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	3,891	22,241
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Condition	3,891	22,241
Financial Instruments	0	0
Cash Collateral Pledged	(829)	(2,884)
Net Amount	3,062	19,357
VOEs
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	3,816	300
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Assets Presented in the Statement of Financial Condition	3,816	300
Financial Instruments	0	0
Cash Collateral Received	(225)	(37)
Net Amount	3,591	263
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	3,830	631
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Condition	3,830	631
Financial Instruments	0	0
Cash Collateral Pledged	(547)	(228)
Net Amount	$ 3,283	$ 403