Investments of Insurance Subsidiaries - Schedule of Maturities of Investments (Detail) $ in Millions	Mar. 31, 2020 USD ($)
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 9
Due after one year through five years, Amortized Cost	100
Due after five years through ten years, Amortized Cost	188
Due after ten years, Amortized Cost	74
Amortized Cost, Total	371
Due in one year or less, Fair Value	9
Due after one year through five years, Fair Value	103
Due after five years through ten years, Fair Value	195
Due after ten years, Fair Value	77
Fair Value, Total	$ 384

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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