Cash, Cash Equivalents, and Marketable Securities - Summary by Major Security Type Cash Cash Equivalents and Marketable Securities Measured at Fair Value on Recurring Basis and Categorized Using Fair Value Hierarchy (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Cash, cash equivalents and marketable securities [Line Items]
Total Estimated Fair Value	$ 7,689		$ 11,448
Less: Restricted cash, cash equivalents, and marketable securities	(290)	[1]	(99)	[1]
Cash
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	2,392
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Estimated Fair Value	2,392		2,595
Cash, cash equivalents, and marketable securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	7,975
Gross Unrealized Gains	8
Gross Unrealized Losses	(4)
Total Estimated Fair Value	7,979		11,547
Level 1 Securities | Money market funds
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	1,760
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Estimated Fair Value	1,760		5,561
Level 1 Securities | Equity securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	3
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Estimated Fair Value	3		2
Level 2 Securities | Foreign government and agency securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	761
Gross Unrealized Gains	3
Gross Unrealized Losses	(1)
Total Estimated Fair Value	763		772
Level 2 Securities | U.S. government and agency securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	2,245
Gross Unrealized Gains	2
Gross Unrealized Losses	(2)
Total Estimated Fair Value	2,245		1,810
Level 2 Securities | Corporate debt securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	708
Gross Unrealized Gains	3
Gross Unrealized Losses	(1)
Total Estimated Fair Value	710		725
Level 2 Securities | Asset-backed securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	66
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Estimated Fair Value	66		49
Level 2 Securities | Other fixed income securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	40
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Estimated Fair Value	$ 40		$ 33

[1] We are required to pledge or otherwise restrict a portion of our cash, cash equivalents, and marketable securities as collateral for standby and trade letters of credit, guarantees, debt, and real estate lease agreements. We classify cash and marketable securities with use restrictions of less than twelve months as “Accounts receivable, net and other” and of twelve months or longer as non-current “Other assets” on our consolidated balance sheets. See “Note 3 — Commitments and Contingencies.”