Consolidated Investment Products (Beginning And Ending Fair Value Measurements For Level 3 Assets And Liabilities) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance (Asset)	$ 46.3	$ 27.2	$ 46.3	$ 27.2	$ 42.3	$ 30.2	$ 24.1	$ 16.2
Purchases (Asset)	2.2	3.0	7.2	7.0
Sales (Asset)	(0.9)	(0.2)	(2.2)	(0.5)
Gains and losses included in the Condensed Consolidated Statements of Income	(2.7)	(0.3)	(11.1)	(4.5)
Ending balance (Asset)	46.3	27.2	46.3	27.2
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net unrealized gains/losses attributable to investments	18.5	26.4	63.4	55.8
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance (Asset)	717.0	702.6	717.0	702.6	711.7	773.9	$ 691.1	$ 500.9
Purchases (Asset)	38.6	58.9	72.7	198.4
Sales (Asset)	(32.3)	(53.7)	(129.2)	(104.1)
Issuances (Asset)	0.0	0.0	0.0	1.8
Settlements (Asset)	0.0	0.0	0.0	0.0
Gains and losses included in the Condensed Consolidated Statements of Income	(1.0)	6.3	8.0	105.6
Transfers to Levels 1 and 2	0.0		(8.4)
Ending balance (Asset)	717.0	702.6	717.0	702.6
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance (Liability)	0.0	(4,301.5)	(5,149.6)	(4,181.7)
Adjustment for adoption of ASU 2014-13					$ 0.0	$ 5,149.6
Purchases (Liability)	0.0	0.0	0.0	0.0
Sales (Liability)	0.0	0.0	0.0	0.0
Issuances (Liability)	0.0	(624.8)	0.0	(1,338.9)
Settlements (Liability)	0.0	212.5	0.0	510.2
Deconsolidation of CIP		0.0		339.0
Net unrealized gains and losses included in other gains and losses	0.0	3.5	0.0	(38.9)
Transfers to Levels 1 and 2	0.0		0.0
Ending balance (Liability)	$ 0.0	$ (4,710.3)	0.0	(4,710.3)
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers to Levels 1 and 2			7.8	0.0
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers to Levels 1 and 2			$ 0.6	$ 0.0