Segment Information - Pre-tax income (loss) from exited business (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Pre-tax income (loss) from exited business:
Change in fair value of funds withheld embedded derivative		$ (626.6)	$ 0.0
Net realized capital gains (losses) on funds withheld assets	[1]	81.0
Total pre-tax income (loss) from exited business		(608.3)
Reconciling Items
Pre-tax income (loss) from exited business:
Change in fair value of funds withheld embedded derivative		(626.6)
Net realized capital gains (losses) on funds withheld assets		81.0
Amortization of reinsurance gain (loss)		(22.1)
Other impacts of reinsured business		(40.6)
Total pre-tax income (loss) from exited business		$ (608.3)

[1] Includes realized and unrealized gains (losses). See Note 3, Investments, for further details.