Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2014

Fair Value Disclosures [Abstract]

Assets and Liabilities Measured at Fair Value on a Recurring Basis

Assets and liabilities measured at fair value on a recurring basis are summarized below (in millions):

			Fair Value Measurement at Reporting Date Using
Description	March 31, 2014		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents:
Money market funds	$	1,876	$	1,876	$	—	$	—
Marketable securities:
U.S. government securities	6,759		6,759		—		—
U.S. government agency securities	2,872		2,872		—		—
Total cash equivalents and marketable securities	$	11,507	$	11,507	$	—	$	—

			Fair Value Measurement at Reporting Date Using
Description	December 31, 2013		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents:
Money market funds	$	2,279	$	2,279	$	—	$	—
Marketable securities:
U.S. government securities	5,687		5,687		—		—
U.S. government agency securities	2,439		2,439		—		—
Total cash equivalents and marketable securities	$	10,405	$	10,405	$	—	$	—