Fair value measurements (Tables)

3 Months Ended

Mar. 31, 2018

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 March 31, 2018 and December 31, 2017 (in thousands):

Description	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
March 31, 2018
Assets:
Cash and cash equivalents	$	456,535	$	329,285	$	127,250	$	—
Marketable securities:
U.S. government agency securities and treasuries		1,096,183		—		1,096,183		—
Certificates of deposit		13,640		—		13,640		—
Total assets	$	1,566,358	$	329,285	$	1,237,073	$	—
Liabilities:
Contingent consideration	$	2,765	$	—	$	—	$	2,765
Total liabilities	$	2,765	$	—	$	—	$	2,765
December 31, 2017
Assets:
Cash and cash equivalents	$	758,505	$	758,505	$	—	$	—
Marketable securities:
U.S. government agency securities and treasuries		838,316		—		838,316		—
Certificates of deposit		17,481		—		17,481		—
Total assets	$	1,614,302	$	758,505	$	855,797	$	—
Liabilities:
Contingent consideration	$	2,231	$	—	$	—	$	2,231
Total liabilities	$	2,231	$	—	$	—	$	2,231

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):

	For the three months ended
	March 31, 2018
Beginning balance	$	2,231
Additions		—
Changes in fair value		534
Payments		—
Ending balance	$	2,765