CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 252.3	$ 236.0	$ 727.3	$ 683.4
Other Comprehensive Income
Change in Net Unrealized Gain on Securities Before Adjustment (net of tax expense of $39.2; $113.9; $334.7; $1,008.1)	66.1	277.2	616.3	1,999.2
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (net of tax benefit of $31.8; $51.7; $261.7; $707.0)	(66.9)	(135.1)	(499.5)	(1,400.3)
Change in Net Gain on Cash Flow Hedges (net of tax benefit of $7.4; $4.3; $19.7; $22.3)	(13.8)	(8.4)	(36.8)	(42.8)
Change in Foreign Currency Translation Adjustment	31.8	(25.8)	88.7	(131.6)
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense of $1.5; $1.7; $4.3; $5.3)	2.2	3.0	6.6	10.1
Total Other Comprehensive Income	19.4	110.9	175.3	434.6
Comprehensive Income	$ 271.7	$ 346.9	$ 902.6	$ 1,118.0