Fair value measurements (Tables)

3 Months Ended

Mar. 31, 2015

Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]

Schedule of Fair Value Classified by Level of Input

The following table summarizes the assets and liabilities measured at fair value on a recurring basis, by level, within the fair value hierarchy (in millions):

	March 31, 2015								December 31, 2014
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	7,683	$	—	$	—	$	7,683	$	7,926	$	—	$	—	$	7,926
Corporate debt securities	—		1,888		—		1,888		—		938		—		938
U.S. treasury securities	1,342		—		—		1,342		363		—		—		363
Residential mortgage and asset-backed securities	—		516		—		516		—		269		—		269
U.S. government agencies securities	—		210		—		210		—		113		—		113
Certificates of deposit	—		71		—		71		—		—		—		—
Non-U.S. government securities	—		37		—		37		—		—		—		—
Municipal debt securities	—		27		—		27		—		16		—		16
Foreign currency derivative contracts	—		607		—		607		—		349		—		349
Deferred compensation plan	61		—		—		61		54		—		—		54
	$	9,086	$	3,356	$	—	$	12,442	$	8,343	$	1,685	$	—	$	10,028
Liabilities:
Contingent consideration	$	—	$	—	$	135	$	135	$	—	$	—	$	133	$	133
Deferred compensation plan	61		—		—		61		54		—		—		54
Foreign currency derivative contracts	—		9		—		9		—		—		—		—
	$	61	$	9	$	135	$	205	$	54	$	—	$	133	$	187

Schedule of Carrying Values and Estimated Fair Values of Debt Instruments

The fair values of our convertible senior notes and senior unsecured notes were determined using Level 2 inputs based on their quoted market values. The following table summarizes the carrying values and fair values of our convertible senior notes and senior unsecured notes (in millions):

		March 31, 2015				December 31, 2014
Type of Borrowing	Description	Carrying Value		Fair Value		Carrying Value		Fair Value
Convertible Senior	May 2016 Notes	$	442	$	1,971	$	483	$	2,097
Senior Unsecured	April 2021 Notes	995		1,166		995		1,108
Senior Unsecured	December 2016 Notes	700		725		700		727
Senior Unsecured	December 2021 Notes	1,248		1,400		1,248		1,377
Senior Unsecured	December 2041 Notes	998		1,271		998		1,229
Senior Unsecured	April 2019 Notes	499		507		499		500
Senior Unsecured	April 2024 Notes	1,747		1,865		1,747		1,836
Senior Unsecured	April 2044 Notes	1,747		2,016		1,747		1,954
Senior Unsecured	February 2020 Notes	499		514		499		504
Senior Unsecured	February 2025 Notes	1,748		1,851		1,748		1,797
Senior Unsecured	February 2045 Notes	1,740		1,947		1,740		1,872