Consolidated Company-Sponsored Investment Funds (Offsetting of Derivative Assets and Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Derivative Asset [Abstract]
Cash Collateral Received	$ (8,500)	$ (300)
VIEs
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	7,892	4,833
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Assets Presented in the Statement of Financial Condition	7,892	4,833
Financial Instruments	0	0
Cash Collateral Received	(7,892)	(1,631)
Net Amount	0	3,202
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	6,603	4,559
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Condition	6,603	4,559
Financial Instruments	0	0
Cash Collateral Pledged	(6,603)	(3,155)
Net Amount	0	1,404
VOEs
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	13,341	4,339
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Assets Presented in the Statement of Financial Condition	13,341	4,339
Financial Instruments	0	0
Cash Collateral Received	(580)	(534)
Net Amount	12,761	3,805
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	12,713	5,083
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Condition	12,713	5,083
Financial Instruments	0	0
Cash Collateral Pledged	(2,797)	(1,201)
Net Amount	$ 9,916	$ 3,882