CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Income	$ 273.5	$ 229.9
Other Comprehensive Income (Loss)
Change in Net Unrealized Gain on Securities Before Adjustment (net of tax expense (benefit) of $(274.9); $89.0)	(1,042.1)	176.9
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (net of tax expense (benefit) of $212.1; $(67.3))	807.9	(134.5)
Change in Net Gain on Hedges (net of tax benefit of $2.3; $6.0)	(8.8)	(10.7)
Change in Foreign Currency Translation Adjustment	47.5	17.1
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense of $0.7; $1.5)	3.1	2.6
Total Other Comprehensive Income (Loss)	(192.4)	51.4
Comprehensive Income	$ 81.1	$ 281.3