CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 245.1	$ 236.8	$ 475.0	$ 447.4
Other Comprehensive Income (Loss)
Change in Net Unrealized Gain on Securities Before Adjustment (net of tax expense of $206.5; $479.9; $295.5; $894.2)	373.3	921.9	550.2	1,722.0
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (net of tax benefit of $162.6; $367.6; $229.9; $655.3)	(298.1)	(699.2)	(432.6)	(1,265.2)
Change in Net Gain on Cash Flow Hedges (net of tax benefit of $6.3; $4.4; $12.3; $18.0)	(12.3)	(8.2)	(23.0)	(34.4)
Change in Foreign Currency Translation Adjustment	39.8	(79.4)	56.9	(105.8)
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense of $1.3; $2.0; $2.8; $3.6)	1.8	4.0	4.4	7.1
Total Other Comprehensive Income	104.5	139.1	155.9	323.7
Comprehensive Income	$ 349.6	$ 375.9	$ 630.9	$ 771.1