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	Mar. 31, 2013		Dec. 31, 2012
Cash, cash equivalents and marketable securities [Line Items]
Total Estimated Fair Value	$ 7,895		$ 11,448
Cash
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	2,228
Total Estimated Fair Value	2,228		2,595
Cash, Cash Equivalents, and Marketable Securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	8,059
Gross Unrealized Gains	14
Gross Unrealized Losses	(2)
Total Estimated Fair Value	8,071		11,547
Restricted Cash, Cash Equivalents and Marketable Securities
Cash, cash equivalents and marketable securities [Line Items]
Total Estimated Fair Value	(176)	[1]	(99)	[1]
Level 1 Securities | Money market funds
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	2,424
Total Estimated Fair Value	2,424		5,561
Level 1 Securities | Equity securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	3
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	679
Gross Unrealized Gains	6
Total Estimated Fair Value	685		772
Level 2 Securities | U.S. government and agency securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	1,983
Gross Unrealized Gains	3
Gross Unrealized Losses	(2)
Total Estimated Fair Value	1,984		1,810
Level 2 Securities | Corporate debt securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	654
Gross Unrealized Gains	5
Total Estimated Fair Value	659		725
Level 2 Securities | Asset-backed securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	55
Total Estimated Fair Value	55		49
Level 2 Securities | Other fixed income securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	33
Total Estimated Fair Value	$ 33		$ 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."