Fair value measurements (Tables)

12 Months Ended

Dec. 31, 2015

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, 2015 and 2014 (in thousands):

Description	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
December 31, 2015
Assets:
Cash and cash equivalents	$	164,269	$	158,269	$	6,000	$	—
Marketable securities:
U.S. government agency securities and    treasuries		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
December 31, 2014
Assets:
Cash and cash equivalents	$	347,845	$	347,845	$	—	$	—
Marketable securities:
U.S. government agency securities		131,536		—		131,536		—
Certificates of deposit		12,622		—		12,622		—
Total assets	$	492,003	$	347,845	$	144,158	$	—
Liabilities:
Contingent consideration	$	6,796	$	—	$	—	$	6,796
Total liabilities	$	6,796	$	—	$	—	$	6,796

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,
	2015			2014
Beginning balance	$	6,796		$	—
Additions		—			6,550
Changes in fair value		2,869			246
Payments		(1,000	)		—
Ending balance	$	8,665		$	6,796