Reclassifications Out of Accumulated Other Comprehensive Income (Loss) - Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	$ (182)	$ 490
Change in other comprehensive income (loss) before reclassifications	(311)	(486)
Reclassifications from accumulated other comprehensive income (loss)	15	(186)
Net current-period other comprehensive income (loss)	(296)	(672)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	(478)	(182)
Unrealized (Loss) on Marketable Securities, Net [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(35)	542
Change in other comprehensive income (loss) before reclassifications	(119)	(436)
Reclassifications from accumulated other comprehensive income (loss)	12	(141)
Net current-period other comprehensive income (loss)	(107)	(577)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	(142)	(35)
Foreign Currency Translation Adjustments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	145	177
Change in other comprehensive income (loss) before reclassifications	(18)	(32)
Net current-period other comprehensive income (loss)	(18)	(32)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	127	145
Pension and Other Post-Retirement Benefit Adjustments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(124)	(276)
Change in other comprehensive income (loss) before reclassifications	(133)	149
Reclassifications from accumulated other comprehensive income (loss)	8	3
Net current-period other comprehensive income (loss)	(125)	152
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	(249)	(124)
Changes in Fair Value of Cash Flow Hedge Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(168)	47
Change in other comprehensive income (loss) before reclassifications	(41)	(167)
Reclassifications from accumulated other comprehensive income (loss)	(5)	(48)
Net current-period other comprehensive income (loss)	(46)	(215)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	$ (214)	$ (168)