Investments of Insurance Subsidiaries - Schedule of Maturities of Investments (Detail) $ in Millions	Mar. 31, 2021 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	144
Due after five years through ten years, Amortized Cost	157
Due after ten years, Amortized Cost	71
Amortized Cost, Total	376
Due in one year or less, Fair Value	4
Due after one year through five years, Fair Value	152
Due after five years through ten years, Fair Value	167
Due after ten years, Fair Value	74
Fair Value, Total	$ 397

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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