Insurance Contracts - Summary of Loss Reserve Roll-Forward, Net of Subrogation Recoverable and Reinsurance (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Loss And Loss Adjustment Expense Reserves [Line Items]
Impact of VIE Consolidation on Gross Loss and Loss Reserves	$ (292)	$ 0
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance of net loss and loss expense reserves	(578)	(430)
Current Year Claims and Claims Adjustment Expense	1	0
Prior Year Claims and Claims Adjustment Expense	23	8
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	24	8
Claim and loss expense payments, net of subrogation and reinsurance	0	0
Claim and loss expense (payments) recoveries, net of subrogation and reinsurance	150	(25)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(150)	25
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	(1)	0
Liability for Unpaid Claims and Claims Adjustment Expense, Net	(404)	(447)	$ (578)	$ (430)
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	49	33	55	33
Policyholder Benefits and Claims Incurred, Ceded	7	1
Net Incurred RMBS Subrogation Recoveries	(224)	(3)
Ceded Loss And Loss Expenses Paid Not Yet Recovered		0
Liability for Claim and Claim Adjustment Expenses Net of Subrogation recoverables	$ (647)	$ (414)	(522)	$ (397)
Financial Guarantee
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Ceded Loss And Loss Expenses Paid Not Yet Recovered			0
Loss Reserves Ceded To Reinsurers			$ 24