CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 396.8	$ 441.0	$ 301.8
Other comprehensive income (loss), before tax:
Unrealized gains (losses) for the period	(6,028.4)	(486.7)	1,332.8
Amortization of present value of future profits and deferred acquisition costs	632.3	35.5	(116.0)
Amount related to premium deficiencies assuming the net unrealized gains (losses) had been realized	165.0	174.5	(204.0)
Reclassification adjustments:
For net realized investment (gains) losses included in net income	60.5	(29.4)	27.1
For amortization of the present value of future profits and deferred acquisition costs related to net realized investment (gains) losses included in net income	(3.4)	1.7	(2.4)
Other comprehensive income (loss) before tax	(5,174.0)	(304.4)	1,037.5
Income tax (expense) benefit related to items of accumulated other comprehensive income (loss)	1,133.8	65.4	(223.9)
Other comprehensive income (loss), net of tax	(4,040.2)	(239.0)	813.6
Comprehensive income (loss)	$ (3,643.4)	$ 202.0	$ 1,115.4