Accounting Policies Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Assets	$ 22,658.2		$ 25,073.2
Liabilities and Equity	22,658.2		$ 25,073.2
Investment Advisory Fees	(913.6)	$ (1,001.4)
Money Market Funds Waiver
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Investment Advisory Fees	(4.9)
Net Waivers	$ (2.6)
Money Market Funds [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Change in Third party distribution service and advisory fee	47.00%
Accounting Standards Update 2015-02 [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Assets	$ 3,170.6
Liabilities and Equity	3,170.6
Consolidated Entities [Member] | Accounting Standards Update 2015-02 [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Assets	458.5
Liabilities and Equity	458.5
Collateralized Loan Obligations [Member] | Accounting Standards Update 2015-02 [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Liabilities and Equity	$ 2,366.5