Summary of Significant Accounting Policies - Schedule of Consolidated Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net (loss) income	$ (213)	$ (1,342)	$ 1,581
Changes in:
Policy benefits and other insurance reserves	2,202	4,445	2,444
Unearned premiums	2,385	2,539	1,608
Deferred policy acquisition costs	(489)	(713)	(624)
Reinsurance recoverables, net	807	451	(1,570)
Income taxes	(229)	(715)	353
Net cash provided by operating activities	$ 4,228	5,121	5,116
As reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net (loss) income		(1,364)	1,566
Changes in:
Policy benefits and other insurance reserves		4,503	2,432
Unearned premiums		2,541	1,618
Deferred policy acquisition costs		(702)	(608)
Reinsurance recoverables, net		408	(1,565)
Income taxes		(721)	349
Net cash provided by operating activities		5,121	5,116
Impact of change
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net (loss) income		22	15
Changes in:
Policy benefits and other insurance reserves		(58)	12
Unearned premiums		(2)	(10)
Deferred policy acquisition costs		(11)	(16)
Reinsurance recoverables, net		43	(5)
Income taxes		6	4
Net cash provided by operating activities		$ 0	$ 0