Reinsurance - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Dec. 31, 2023
Ceded Credit Risk [Line Items]
Investments	$ 125,153.0	$ 125,153.0	$ 117,325.0
Other investments	5,470.0	5,470.0	4,757.0
Deposit assets, net of allowance for credit losses	28,942.0	28,942.0	21,056.0
LPINE
Ceded Credit Risk [Line Items]
Deposits assets	6,500.0	6,500.0
Investments	10,500.0	10,500.0
LPINE | Fixed Annuities
Ceded Credit Risk [Line Items]
Reinsurance recoverables	4,100.0	4,100.0
Reinsurance recoverables on unpaid losses	14.0	14.0
LNBAR
Ceded Credit Risk [Line Items]
Reinsurance recoverables	13,400.0	13,400.0	13,200.0
Reinsurance recoverables on unpaid losses	4,100.0	4,100.0	4,200.0
Reinsurance recoverable for unpaid claims, amortization	42.0	125.0
Other investments	871.0	871.0	1,200.0
Trust funded to support reinsurance receivable	13,000.0	13,000.0	13,000.0
Fortitude Re | Fixed Annuities
Ceded Credit Risk [Line Items]
Reinsurance recoverables	10,700.0	10,700.0	10,500.0
Reinsurance recoverables on unpaid losses	2,600.0	2,600.0	2,700.0
Reinsurance recoverable for unpaid claims, amortization	23.0	67.0
Deposit assets, net of allowance for credit losses	$ 3,400.0	$ 3,400.0	$ 4,200.0