CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net Income	$ 182.9	$ 265.5	$ 335.9	$ 426.5
Other Comprehensive Income (Loss)
Change in Net Unrealized Gain on Securities Before Adjustment (net of tax expense (benefit) of $226.9; $653.9; $(207.3); $217.4)	858.8	2,507.7	(787.2)	841.0
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (net of tax expense (benefit) of $(165.8); $(510.6); $166.0; $(129.8))	(625.6)	(1,939.9)	630.9	(493.8)
Change in Net Gain on Hedges (net of tax benefit of $—; $7.1; $5.4; $0.5)	0.4	(24.4)	(20.3)	(1.6)
Change in Foreign Currency Translation Adjustment (net of tax expense (benefit) of $(0.2); $2.9; $1.6; $0.8)	9.3	(3.0)	16.6	(66.6)
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense of $1.2; $1.1; $2.4; $3.0)	(4.1)	(3.9)	(7.9)	(10.9)
Net Other Comprehensive Income (Loss)	247.0	544.3	(152.1)	289.9
Comprehensive Income	$ 429.9	$ 809.8	$ 183.8	$ 716.4