Investments of Insurance Subsidiaries - Schedule of Maturities of Investments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014
Amortized Cost and Fair Value Debt Securities [Abstract]
Due in one year or less, Amortized Cost	$ 59
Due after one year through five years, Amortized Cost	207
Due after five years through ten years, Amortized Cost	97
Due after ten years, Amortized Cost	123
Amortized Cost, Total	486
Due in one year or less, Fair Value	60
Due after one year through five years, Fair Value	212
Due after five years through ten years, Fair Value	104
Due after ten years, Fair Value	128
Fair Value, Total	$ 504