CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 105.0	$ 99.8	$ 353.4	$ 325.2
Other comprehensive loss, before tax:
Unrealized losses on investments	(1,407.2)	(112.9)	(6,128.2)	(436.6)
Adjustment to present value of future profits and deferred acquisition costs	126.2	13.4	666.5	21.6
Amount related to premium deficiencies assuming the net unrealized gains had been realized	0.0	16.5	165.0	114.0
Reclassification adjustments:
For net realized investment (gains) losses included in net income	1.0	(0.9)	36.0	(26.4)
For amortization of the present value of future profits and deferred acquisition costs related to net realized investment (gains) losses included in net income	(0.6)	0.1	(1.7)	1.4
Other comprehensive loss before tax	(1,280.6)	(83.8)	(5,262.4)	(326.0)
Income tax benefit related to items of accumulated other comprehensive loss	279.9	18.0	1,149.6	69.6
Other comprehensive loss, net of tax	(1,000.7)	(65.8)	(4,112.8)	(256.4)
Comprehensive income (loss)	$ (895.7)	$ 34.0	$ (3,759.4)	$ 68.8