Fair value measurements (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Recorded Amount of Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table sets forth the Company’s assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2016 and 2015 (in thousands):

Description	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
December 31, 2016
Assets:
Cash and cash equivalents	$	278,887	$	278,887	$	—	$	—
Marketable securities:
U.S. government agency securities and    treasuries		599,460		—		599,460		—
Certificates of deposit		6,483		—		6,483		—
Total assets	$	884,830	$	278,887	$	605,943	$	—
Liabilities:
Contingent consideration	$	7,756	$	—	$	—	$	7,756
Total liabilities	$	7,756	$	—	$	—	$	7,756
December 31, 2015
Assets:
Cash and cash equivalents	$	164,269	$	158,269	$	6,000	$	—
Marketable securities:
U.S. government agency securities		687,147		—		687,147		—
Certificates of deposit		14,347		—		14,347		—
Total assets	$	865,763	$	158,269	$	707,494	$	—
Liabilities:
Contingent consideration	$	8,665	$	—	$	—	$	8,665
Total liabilities	$	8,665	$	—	$	—	$	8,665

Roll-Forward of Fair Value of the Company's Contingent Consideration Obligations

The table below provides a roll-forward of fair value of the Company’s contingent consideration obligations which include Level 3 inputs (in thousands):

	Year ended December 31,
	2016			2015
Beginning balance	$	8,665		$	6,796
Additions		—			—
Changes in fair value		4,091			2,869
Payments		(5,000	)		(1,000	)
Ending balance	$	7,756		$	8,665