Long-Term Debt - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Nov. 30, 2012
Debt Instrument [Line Items]
Unamortized discount on senior notes		$ 89,000,000	$ 96,000,000
Other long-term debt carrying amount including current portion		312,000,000	881,000,000
Total estimated fair value of senior notes		$ 8,500,000,000	$ 9,100,000,000
Other debt, weighted average interest rate		3.70%	5.50%
Credit Agreement, initiation date	Sep. 05, 2014
Credit Agreement, maximum borrowing capacity		$ 2,000,000,000
Credit Agreement, term		2 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
Credit Agreement, basis spread on variable rate		0.625%
Credit Agreement, borrowings outstanding		$ 0	$ 0
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
Maximum
Debt Instrument [Line Items]
Credit Agreement, basis spread on variable rate		1.00%