Consolidated Company-Sponsored Investment Funds - Offsetting of Derivative Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivative Asset [Abstract]
Cash Collateral Received	$ (1,000)	$ (300)
VIEs
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	1,299	4,833
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Assets Presented in the Statement of Financial Condition	1,299	4,833
Financial Instruments	0	0
Cash Collateral Received	(301)	(1,631)
Net Amount	998	3,202
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	4,391	4,559
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Condition	4,391	4,559
Financial Instruments	0	0
Cash Collateral Pledged	(3,697)	(3,155)
Net Amount	694	1,404
VOEs
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	3,574	4,339
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Assets Presented in the Statement of Financial Condition	3,574	4,339
Financial Instruments	0	0
Cash Collateral Received	(985)	(534)
Net Amount	2,589	3,805
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	1,155	5,083
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Condition	1,155	5,083
Financial Instruments	0	0
Cash Collateral Pledged	(1,155)	(1,201)
Net Amount	0	$ 3,882
Variable Interest Entity, Not Primary Beneficiary
Derivative [Line Items]
Net assets	$ 68,900,000