Supplemental Cash Flow Information - Supplemental Cash Flow Reconciliation (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended			48 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Supplemental Cash Flow Information [Abstract]
Interest expense	$ (2,670)	$ (2,252)	$ (2,100)	$ (7,000)
Adjustments to reconcile to cash paid for interest:
Net change in accrued interest	(346)	(156)	(42)
Executive compensation and benefit plans	(13)	(16)	(18)
Capitalized interest	45	38	38
Amortization of deferred finance costs and debt discount/premium	(438)	(360)	(315)
Amortization of accumulated other comprehensive loss	0	(5)	(29)
Rollover of PIK interest to principal	(2)	(1)	(1)
Change in derivative instruments due to cash settlements	160	138	30
Other	(6)	9	9
Cash paid for interest	$ 2,070	$ 1,899	$ 1,772	$ (5,700)