Capital Structure - Components of Accumulated Other Comprehensive Loss (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)
Equity [Abstract]
Unrealized gains on available-for-sale securities, beginning balances	$ 13
Unrealized losses on available-for-sale securities, net of income tax benefit	(2)
Unrealized gains on available-for-sale securities, ending balances	11
Foreign currency translation adjustments, beginning balances	(36)
Foreign currency translation adjustments	(24)
Foreign currency translation adjustments, ending balances	(60)
Defined benefit plans, beginning balances	(174)
Defined benefit plans, (income) expense reclassified into operations from other comprehensive income	11
Defined benefit plans, ending balances	(163)
Change in fair value of derivative instruments, beginning balances	(126)
Change in fair value of derivative instruments	(30)
Change in fair value of derivatives instruments, (income) expense reclassified into operations from other comprehensive income	59
Change in fair value of derivative instruments, ending balances	(97)
Accumulated other comprehensive income, net of tax, beginning balances	(323)
Unrealized losses on available-for-sale securities, net of income tax benefit	(2)
Foreign currency translation adjustments	(24)
Change in fair value of derivative instruments	(30)
Expense reclassified into operations from other comprehensive income, Total	70
Accumulated other comprehensive income (loss), net of tax, ending balances	$ (309)