Investments of Insurance Subsidiaries - Schedule of Maturities of Investments (Detail) $ in Millions	Sep. 30, 2023 USD ($)
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 13
Due after one year through five years, Amortized Cost	148
Due after five years through ten years, Amortized Cost	165
Due after ten years, Amortized Cost	78
Amortized Cost, Total	404
Due in one year or less, Fair Value	13
Due after one year through five years, Fair Value	139
Due after five years through ten years, Fair Value	140
Due after ten years, Fair Value	69
Fair Value, Total	$ 361