Nature of Operations and Significant Accounting Policies - Pre-tax Impacts To Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Increase to income before taxes
Deferred acquisition costs amortization	$ 4.0	$ (34.3)	$ (326.5)	$ (192.8)
Cost of reinsurance amortization	(15.8)	3.5	(59.5)	11.1
Income (loss) before income taxes	$ 1,730.1	$ 428.1	6,055.2	$ 1,474.6
Actuarial Balance Re-Cohorting
Increase to income before taxes
Deferred acquisition costs amortization			(106.6)
Cost of reinsurance amortization			4.2
Unearned revenue liability amortization			32.4
Change in additional liability for certain benefit features			139.7
Income (loss) before income taxes			69.7
Increase to pre-tax other comprehensive income
Deferred acquisition cost unrealized losses			(5.6)
Cost of reinsurance unrealized gains			8.7
Unearned revenue liability unrealized gains			8.5
Change in additional liability for certain benefit features unrealized gains			24.3
Total increase to pre-tax other comprehensive income			35.9
Total increase to pre-tax comprehensive income			$ 105.6