CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 523.4	$ 994.2	$ 931.4
Other Comprehensive Income (Loss)
Change in Net Unrealized Gain on Securities Before Adjustment (net of tax expense (benefit) of $(614.2); $328.1; $318.0	(2,314.5)	721.7	661.9
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (net of tax expense (benefit) of $371.7; $(245.0); $(200.6)	1,411.8	(554.5)	(425.6)
Change in Net Gain on Hedges (net of tax benefit of $8.2; $24.4; $25.4)	(31.7)	(45.2)	(50.5)
Change in Foreign Currency Translation Adjustment (net of tax benefit of $0.6; $-; $-)	(50.7)	99.5	(180.4)
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense (benefit) of $17.0; $(8.3); $(34.2))	60.9	(43.0)	(72.5)
Total Other Comprehensive Income (Loss)	(924.2)	178.5	(67.1)
Comprehensive Income	$ (400.8)	$ 1,172.7	$ 864.3