Consolidated Investment Products Consolidated Investment Products (Adoption of ASU 2015-02) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Item Effected [Line Items]
Cash and cash equivalents of consolidated investment products	$ 167.8	$ 363.3
Accounts receivable and other assets of consolidated investment products	139.6	173.5
Investments Of Consolidated Investment Products	3,639.4	6,016.1
Total assets	22,658.2	25,073.2
Debt of CIP	3,061.2	5,437.0
Other liabilities of consolidated investment products	181.5	273.7
Total liabilities	14,288.4	16,210.2
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	7,962.5	8,695.7	$ 8,872.8	$ 9,119.8
Total liabilities and equity	22,658.2	$ 25,073.2
Accounting Standards Update 2015-02 [Member]
Item Effected [Line Items]
Cash and cash equivalents of consolidated investment products	163.8
Accounts receivable and other assets of consolidated investment products	68.8
Investments Of Consolidated Investment Products	2,938.0
Total assets	3,170.6
Debt of CIP	2,259.2
Other liabilities of consolidated investment products	110.4
Total liabilities	2,369.6
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	801.0
Total liabilities and equity	3,170.6
Consolidated Entities [Member] | Accounting Standards Update 2015-02 [Member]
Item Effected [Line Items]
Cash and cash equivalents of consolidated investment products	33.8
Accounts receivable and other assets of consolidated investment products	105.4
Investments Of Consolidated Investment Products	319.3
Total assets	458.5
Debt of CIP	0.0
Other liabilities of consolidated investment products	102.4
Total liabilities	102.4
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	356.1
Total liabilities and equity	$ 458.5