Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (12.0)	$ 104.9
Changes in net unrealized gains (losses) on investment securities:
Having no credit losses recognized in the Consolidated Statements of Income	93.3	(379.4)
Having credit losses recognized in the Consolidated Statements of Income	1.0	(0.5)
Total available-for-sale securities	94.3	(379.9)
Pension and postretirement benefits:
Net change in net actuarial loss	1.6	1.1
Long-duration insurance contracts:
Net change in market risk	(2.1)	6.9
Other comprehensive income (loss), net of tax	93.8	(371.9)
Comprehensive income (loss)	$ 81.8	$ (267.0)