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Investments - Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments (Detail) - USD ($) $ in Millions | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 2,041 |
Gross Unrealized Gains | 31 | $ 141
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 106 | 16
Available-for-sale Securities, Current | 1,966 | 2,265
Available-for-sale Securities | 1,966 |
Available-for-sale Securities, Amortized Cost Basis | 2,041 | 2,140
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 106 | 16
Short-term Investments [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 0 | 0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 | 0
Available-for-sale Securities | 507 | 414
Available-for-sale Securities, Amortized Cost Basis | 507 | 415
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 0 | 0
Fixed Income Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 1,469 | 1,605
Gross Unrealized Gains | 31 | 141
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 106 | 16
Available-for-sale Securities | 1,395 | 1,730
Available-for-sale Securities, Amortized Cost Basis | 1,469 | 1,605
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 106 | 16
Fixed Income Securities [Member] | Municipal Bonds [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 0 | 28
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 2 | 3
Available-for-sale Securities | 43 | 340
Available-for-sale Securities, Amortized Cost Basis | 44 | 315
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 2 | 3
Fixed Income Securities [Member] | Corporate Obligations [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 1 | 10
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 63 | 9
Available-for-sale Securities | 598 | 613
Available-for-sale Securities, Amortized Cost Basis | 659 | 612
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 63 | 9
Fixed Income Securities [Member] | Debt Security, Government, Non-US [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 0 | 0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 9 | 2
Available-for-sale Securities | 76 | 87
Available-for-sale Securities, Amortized Cost Basis | 85 | 89
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 9 | 2
Fixed Income Securities [Member] | U.S. Government Obligations [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 0 | 1
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 4 | 1
Available-for-sale Securities | 65 | 45
Available-for-sale Securities, Amortized Cost Basis | 68 | 45
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 4 | 1
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 230 |
Gross Unrealized Gains | 28 | 70
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 19 | 0
Available-for-sale Securities | 238 | 252
Available-for-sale Securities, Amortized Cost Basis | 230 | 182
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 19 | 0
Fixed Income Securities [Member] | Collateralized Debt Obligations [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 141 |
Gross Unrealized Gains | 0 | 0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 4 | 0
Available-for-sale Securities | 137 | 128
Available-for-sale Securities, Amortized Cost Basis | 141 | 128
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 4 | 0
Fixed Income Securities [Member] | Asset-backed Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 227 |
Gross Unrealized Gains | 2 | 32
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 5 | 0
Available-for-sale Securities | 224 | 265
Available-for-sale Securities, Amortized Cost Basis | 227 | 234
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | $ 5 | 0
Dbt Securities Available for Sale Unrealized Loss Measured as a Percent of Amortized Cost | 2.00% |
Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 15 |
Gross Unrealized Gains | 0 |
Available-for-sale Securities | 15 |
Available-for-sale Securities, Amortized Cost Basis | 15 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 |
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 0 |
Fixed Income Securities [Member] | Collateralized Mortgage Backed Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 |
Available-for-sale Securities, Amortized Cost Basis | 15 |
Fixed Income Investments And Other Investments [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 31 | 141
Available-for-sale Securities | 1,902 | 2,145
Available-for-sale Securities, Amortized Cost Basis | 1,977 | 2,020
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 106 | 16
Collateral Pledged [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale Securities | 64 | 120
Collateral Pledged [Member] | Fixed Income Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 0 | 15
Gross Unrealized Gains | 0 | 0
Available-for-sale Securities | 0 | 15
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 0 | 0
Collateral Pledged [Member] | Fixed Income Securities [Member] | Short-term Investments [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 0 | 0
Available-for-sale Securities | 64 | 105
Available-for-sale Securities, Amortized Cost Basis | 64 | 105
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 0 | 0
Collateral Pledged [Member] | Fixed Income Securities [Member] | US Treasury and Government |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains |  | 0
Available-for-sale Securities |  | 15
Available-for-sale Securities, Amortized Cost Basis |  | 15
Debt Securities, Available-for-sale, Allowance for Credit Loss |  | 0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax |  | 0
Asset Pledged as Collateral [Member] | Fixed Income Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 64 | 120
Debt Securities, Available-for-sale, Allowance for Credit Loss | $ 0 | $ 0

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