Long-Term Debt - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Nov. 30, 2012
Debt Instrument [Line Items]
Long-term capital lease obligations	$ 5,080,000,000	$ 4,212,000,000
Credit Facility and Other Long Term Debt	588,000,000	312,000,000
Debt Instrument Face Amount Outstanding	8,300,000,000
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	90,000,000	97,000,000
Other long-term debt carrying amount including current portion	93,000,000	312,000,000
Total estimated fair value of senior notes	$ 8,700,000,000	$ 8,500,000,000
Other debt, weighted average interest rate	3.40%	3.70%
Credit Agreement, borrowings outstanding	$ 0	$ 0
Finance Lease Obligations Current	144,000,000	99,000,000
Long-term finance lease obligations	$ 2,439,000,000	1,736,000,000
Notes issued in 2014
Debt Instrument [Line Items]
Issued notes			$ 6,000,000,000
Interest payment frequency	semi-annually in arrears in June and December
Notes issued in 2012
Debt Instrument [Line Items]
Issued notes				$ 3,000,000,000
Interest payment frequency	semi-annually in arrears in May and November
October 2016 Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Other debt, weighted average interest rate	2.30%
Debt Instrument, Collateral Amount	$ 579,000,000
Credit Agreement, maximum borrowing capacity	$ 500,000,000
Credit Agreement, term	3 years
Credit Agreement, term additional information	secured by certain seller receivables
Credit Agreement, basis spread on variable rate	1.65%
Line of Credit Facility, Commitment Fee Percentage	0.50%
Credit Agreement, borrowings outstanding	$ 495,000,000	$ 0
May 2016 Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit Agreement, maximum borrowing capacity	$ 3,000,000,000
Credit Agreement, term	3 years
Credit Agreement, term additional information	may be extended for up to three additional one-year terms if approved by the lenders
Credit Agreement, variable rate basis	LIBOR
May 2016 Revolving Credit Facility [Member] | Minimum
Debt Instrument [Line Items]
Credit Agreement, basis spread on variable rate	0.60%
Line of Credit Facility, Commitment Fee Percentage	0.05%
May 2016 Revolving Credit Facility [Member] | Maximum
Debt Instrument [Line Items]
Credit Agreement, basis spread on variable rate	1.00%
Line of Credit Facility, Commitment Fee Percentage	0.09%