CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net Income	$ 231.1	$ 242.0	$ 657.6	$ 804.1
Other Comprehensive Income (Loss)
Change in Net Unrealized Gain on Securities Before Adjustment (net of tax expense of $126.6; $209.5; $344.0; $815.6)	481.4	800.4	1,322.4	3,093.2
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (net of tax benefit of $89.9; $172.6; $219.7; $619.3)	(340.0)	(665.2)	(833.8)	(2,358.7)
Change in Net Gain on Hedges (net of tax benefit of $6.7; $3.7; $7.2; $12.3)	(27.5)	(13.7)	(29.1)	(46.3)
Change in Foreign Currency Translation Adjustment (net of tax expense (benefit) of $(1.9); $0.8; $(1.1); $1.2)	34.5	(37.6)	(32.1)	(40.0)
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense of $0.4; $0.8; $3.4; $2.8)	(2.0)	(5.4)	(12.9)	(12.8)
Net Other Comprehensive Income (Loss)	150.4	89.3	440.3	661.0
Comprehensive Income	381.5	331.3	1,097.9	1,465.1
Change in Net Unrealized Gain on Securities Before Adjustment, Tax Expense	126.6	209.5	344.0	815.6
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance, Tax Benefit	(89.9)	(172.6)	(219.7)	(619.3)
Change in Net Gain on Hedges, Tax Benefit	(6.7)	(3.7)	(7.2)	(12.3)
Change in Foreign Currency Translation Adjustment, Tax Expense (Benefit)	(1.9)	0.8	(1.1)	1.2
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	$ 0.4	$ 0.8	$ 3.4	$ 2.8