Consolidated Company-Sponsored Investment Funds (Offsetting of Derivative Assets and Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Derivative Asset [Abstract]
Cash Collateral Received	$ (2,400)	$ (500)
VIEs
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	31,006	30,636
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	31,006	30,636
Financial Instruments	0	0
Cash Collateral Received	(2,271)	(194)
Net Amount	28,735	30,442
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	18,400	22,241
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	18,400	22,241
Financial Instruments	0	0
Cash Collateral Pledged	(1,372)	(2,884)
Net Amount	17,028	19,357
VOEs
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	638	300
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	638	300
Financial Instruments	0	0
Cash Collateral Received	(47)	(37)
Net Amount	591	263
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	676	631
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	676	631
Financial Instruments	0	0
Cash Collateral Pledged	(253)	(228)
Net Amount	$ 423	$ 403