Investments of Insurance Subsidiaries - Schedule of Maturities of Investments (Detail) $ in Millions	Dec. 31, 2016 USD ($)
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 91
Due after one year through five years, Amortized Cost	95
Due after five years through ten years, Amortized Cost	159
Due after ten years, Amortized Cost	28
Amortized Cost, Total	373
Due in one year or less, Fair Value	91
Due after one year through five years, Fair Value	97
Due after five years through ten years, Fair Value	165
Due after ten years, Fair Value	28
Fair Value, Total	$ 381