CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net Income	$ 931.4	$ 867.1	$ 402.1
Other Comprehensive Income (Loss)
Change in Net Unrealized Gain on Securities Before Adjustment (net of tax expense (benefit) of $318.0; $(892.5); $725.8)	661.9	(1,720.9)	1,439.3
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (net of tax expense (benefit) of $(200.6); $856.6; $(665.1))	(425.6)	1,634.9	(1,284.7)
Change in Net Gain on Cash Flow Hedges (net of tax benefit of $25.4; $4.3; $2.0)	(50.5)	(13.0)	(5.3)
Change in Foreign Currency Translation Adjustment (net of tax benefit of $-; $0.1; $-)	(180.4)	(60.2)	(66.3)
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense (benefit) of $(34.2); $3.2; $(92.4))	(72.5)	8.9	(171.6)
Total Other Comprehensive Loss	(67.1)	(150.3)	(88.6)
Comprehensive Income	$ 864.3	$ 716.8	$ 313.5