Long-Term Debt - Additional Information (Detail) - USD ($)	3 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Nov. 30, 2012
Debt Instrument [Line Items]
Unamortized discount	$ 93,000,000	$ 96,000,000
Carrying amount of other long-term debt including current portion	602,000,000	881,000,000
Total estimated fair value of notes	$ 9,000,000,000	$ 9,100,000,000
Other long-term debt, weighted average interest rate	4.30%	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
Issued in December 2014
Debt Instrument [Line Items]
Face amount		$ 6,000,000,000
Interest payment frequency	semi-annually in arrears in June and December
Issued in November 2012
Debt Instrument [Line Items]
Face amount			$ 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%