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

Debt Securities Available for Sale Unrealized Loss Measured as a Percent of Amortized Cost

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- Definition

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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