Investments of Insurance Subsidiaries - Schedule of Maturities of Investments (Detail) $ in Millions	Dec. 31, 2020 USD ($)
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 4
Due after one year through five years, Amortized Cost	147
Due after five years through ten years, Amortized Cost	157
Due after ten years, Amortized Cost	76
Amortized Cost, Total	384
Due in one year or less, Fair Value	4
Due after one year through five years, Fair Value	156
Due after five years through ten years, Fair Value	174
Due after ten years, Fair Value	82
Fair Value, Total	$ 416

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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