Consolidated Company-Sponsored Investment Funds (Offsetting of Derivative Assets and Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Derivative Asset [Abstract]
Cash Collateral Received	$ (300)	$ (500)
VIEs
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	2,628	30,636
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	2,628	30,636
Financial Instruments	0	0
Cash Collateral Received	(240)	(194)
Net Amount	2,388	30,442
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	2,986	22,241
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	2,986	22,241
Financial Instruments	0	0
Cash Collateral Pledged	(1,089)	(2,884)
Net Amount	1,897	19,357
VOEs
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	856	300
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	856	300
Financial Instruments	0	0
Cash Collateral Received	(136)	(37)
Net Amount	720	263
Derivative Liability [Abstract]
Gross Amounts of Recognized Liabilities	531	631
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	531	631
Financial Instruments	0	0
Cash Collateral Pledged	(531)	(228)
Net Amount	$ 0	$ 403