Consolidated Company-Sponsored Investment Funds (Offsetting of Derivative Assets and Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Derivative Asset [Abstract]
Cash Collateral Received	$ (1,100)	$ (4,800)
VIEs
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	2,624	3,410
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	2,624	3,410
Financial Instruments	0	0
Cash Collateral Received	(958)	(856)
Net Amount	1,666	2,554
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	2,780	3,891
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	2,780	3,891
Financial Instruments	0	0
Cash Collateral Pledged	(2,089)	(829)
Net Amount	691	3,062
VOEs
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	4,360	3,816
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	4,360	3,816
Financial Instruments	0	0
Cash Collateral Received	(241)	(225)
Net Amount	4,119	3,591
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	3,938	3,830
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	3,938	3,830
Financial Instruments	0	0
Cash Collateral Pledged	(913)	(547)
Net Amount	$ 3,025	$ 3,283