Consolidated Investment Products (Beginning And Ending Fair Value Measurements For Level 3 Assets And Liabilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net unrealized gains/losses attributable to investments	$ 1.3	$ (29.4)
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance (Asset)	388.6	363.9
Purchases (Asset)	39.4	96.1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0.0	(42.1)
Net unrealized gains and losses included in other gains and losses (Liability)	1.3	(20.9)
Transfers to Level 2	0.0	(8.4)
Ending balance (Asset)	40.7	388.6
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance (Liability)	0.0	(5,149.6)
Purchases (Liability)	0.0	0.0
Sales (Liability)	0.0	0.0
Gains and losses included in the Consolidated Statements of Income (Liability)	0.0	0.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net	0.0	0.0
Ending balance (Liability)	0.0	0.0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers to Level 2		7.8
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers to Level 2	0.6
Accounting Standards Update 2014-13 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption			$ (17.6)
Accounting Standards Update 2014-13 [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Increase (Decrease) for Accounting Pronouncements	0.0	0.0
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Increase (Decrease) for Accounting Pronouncements	0.0	5,149.6
Accounting Standards Update 2015-02 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption		(733.5)
Accounting Standards Update 2015-02 [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Increase (Decrease) for Accounting Pronouncements	388.6	0.0
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Increase (Decrease) for Accounting Pronouncements	$ 0.0	$ 0.0