Investments - Summary of Sources of Collateral Received and Various Investment Agreement in which Collateral Pledged (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Investment [Line Items]
Fair Value Of Securities Deposited With Governmental Authorities	$ 23	$ 23
Fair Value of Securities Deposited in Connection wtih Letter of Credit	1	1
Standard & Poor's, B Rating [Member]
Investment [Line Items]
Investment Owned, at Fair Value	401	403
Standard & Poor's, B Rating [Member] | Municipal Bonds [Member]
Investment [Line Items]
Investment Owned, at Fair Value	10	10
Standard & Poor's, B Rating [Member] | Mortgage And Other Asset Backed Securities [Member]
Investment [Line Items]
Investment Owned, at Fair Value	392	394
Ambac Assurance Corporation [Member] | Standard & Poor's, B Rating [Member]
Investment [Line Items]
Investment Owned, at Fair Value	401	403
Ambac Assurance Corporation [Member] | Standard & Poor's, B Rating [Member] | Municipal Bonds [Member]
Investment [Line Items]
Investment Owned, at Fair Value	10	10
Ambac Assurance Corporation [Member] | Standard & Poor's, B Rating [Member] | Mortgage And Other Asset Backed Securities [Member]
Investment [Line Items]
Investment Owned, at Fair Value	$ 392	$ 394