Fair value measurements (Tables)

6 Months Ended

Jun. 30, 2014

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

Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block]

The following table summarizes the carrying values and fair values of our convertible senior notes and senior unsecured notes (in thousands):

		June 30, 2014				December 31, 2013
Type of Borrowing	Description	Carrying Value		Fair Value		Carrying Value		Fair Value
Convertible Senior	May 2014 Notes	$	—	$	—	$	234,217	$	783,651
Convertible Senior	May 2016 Notes	822,139		3,084,363		1,113,043		3,871,516
Senior Unsecured	April 2021 Notes	994,210		1,099,010		993,781		1,075,480
Senior Unsecured	December 2014 Notes	749,868		756,195		749,710		762,637
Senior Unsecured	December 2016 Notes	699,441		734,146		699,326		740,705
Senior Unsecured	December 2021 Notes	1,247,861		1,375,563		1,247,716		1,336,738
Senior Unsecured	December 2041 Notes	997,923		1,171,090		997,885		1,118,660
Senior Unsecured	April 2019 Notes	499,189		500,985		—		—
Senior Unsecured	April 2024 Notes	1,747,271		1,798,843		—		—
Senior Unsecured	April 2044 Notes	1,746,641		1,853,028		—		—

Schedule of Fair Value Classified by Level of Input [Table Text Block]

The following table summarizes, for assets or liabilities recorded at fair value, the respective fair value and the classification by level of input within the fair value hierarchy previously defined (in thousands):

	June 30, 2014								December 31, 2013
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Assets:
Debt securities:
Money market funds	$	5,892,347	$	—	$	—	$	5,892,347	$	1,490,964	$	—	$	—	$	1,490,964
Corporate debt securities	—		347,545		—		347,545		—		220,025		—		220,025
U.S. treasury securities	365,061		—		—		365,061		85,403		—		—		85,403
U.S. government agencies securities	—		41,668		—		41,668		—		93,350		—		93,350
Residential mortgage and asset-backed securities	—		87,358		—		87,358		—		46,941		—		46,941
Municipal debt securities	—		9,229		—		9,229		—		12,065		—		12,065
Total debt securities	6,257,408		485,800		—		6,743,208		1,576,367		372,381		—		1,948,748
Deferred compensation plan	49,827		—		—		49,827		44,461		—		—		44,461
Derivatives	—		22,874		—		22,874		—		13,879		—		13,879
	$	6,307,235	$	508,674	$	—	$	6,815,909	$	1,620,828	$	386,260	$	—	$	2,007,088
Liabilities:
Contingent consideration	$	—	$	—	$	271,726	$	271,726	$	—	$	—	$	263,760	$	263,760
Derivatives	—		40,472		—		40,472		—		99,057		—		99,057
Deferred compensation plan	49,827		—		—		49,827		44,461		—		—		44,461
	$	49,827	$	40,472	$	271,726	$	362,025	$	44,461	$	99,057	$	263,760	$	407,278

Fair Value Rollforward of Contingent Consideration Liabilities [Table Text Block]

The following table provides a rollforward of our contingent consideration liabilities, which are recorded as part of other accrued liabilities and other long-term obligations in our Condensed Consolidated Balance Sheets (in thousands):

Balance at December 31, 2013	$	263,760
Additions from new acquisitions	—
Net changes in valuation	7,966
Balance at June 30, 2014	$	271,726