Schedule I - Investments (Detail) $ in Millions	Dec. 31, 2023 USD ($)
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	$ 2,064
Fair Value	1,931
Amount at which shown in the balance sheet	1,931
Other Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	3
Fair Value	3
Amount at which shown in the balance sheet	3
Assets Of Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	67
Fair Value	57
Amount at which shown in the balance sheet	57
Loans Receivable [Member] | Assets Of Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	47
Fair Value	35
Amount at which shown in the balance sheet	35
Long-Term Available-For-Sale [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,175
Fair Value	1,043
Amount at which shown in the balance sheet	1,043
Long-Term Available-For-Sale [Member] | U.S. Treasury And Government Agency [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	214
Fair Value	198
Amount at which shown in the balance sheet	198
Long-Term Available-For-Sale [Member] | US States And Political Subdivisions [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	128
Fair Value	123
Amount at which shown in the balance sheet	123
Long-Term Available-For-Sale [Member] | Foreign Governments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	13
Fair Value	11
Amount at which shown in the balance sheet	11
Long-Term Available-For-Sale [Member] | Corporate Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	504
Fair Value	417
Amount at which shown in the balance sheet	417
Short-Term Available-For-Sale [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	513
Fair Value	514
Amount at which shown in the balance sheet	514
AFS Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,688
Fair Value	1,557
Amount at which shown in the balance sheet	1,557
Investments At Fair Value [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	373
Fair Value	371
Amount at which shown in the balance sheet	371
Investments At Fair Value [Member] | Assets Of Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	20
Fair Value	22
Amount at which shown in the balance sheet	22
Mortgage-backed [Member] | Long-Term Available-For-Sale [Member] | Residential Mortgage backed Agency [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	149
Fair Value	135
Amount at which shown in the balance sheet	135
Mortgage-backed [Member] | Long-Term Available-For-Sale [Member] | Residential Mortgage-Backed Non Agency [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	31
Fair Value	26
Amount at which shown in the balance sheet	26
Mortgage-backed [Member] | Long-Term Available-For-Sale [Member] | Commercial Mortgage-Backed [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	14
Fair Value	13
Amount at which shown in the balance sheet	13
Asset-backed [Member] | Long-Term Available-For-Sale [Member] | Collateralized Debt Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	96
Fair Value	95
Amount at which shown in the balance sheet	95
Asset-backed [Member] | Long-Term Available-For-Sale [Member] | Other Asset-Backed [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	26
Fair Value	25
Amount at which shown in the balance sheet	$ 25