Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Schedule of fair value of assets and liabilities measured on recurring basis

The following tables set forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands):

	March 31, 2018
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	169,430	$	—	$	—	$	169,430
U.S. government agencies	—		74,922		—		74,922
Corporate debt securities	—		296,098		—		296,098
Derivative assets	—		833		—		833
Total	$	169,430	$	371,853	$	—	$	541,283
Liabilities:
Derivative liabilities	$	—	$	430	$	—	$	430
Stock warrant liability	—		—		164		164
Total	$	—	$	430	$	164	$	594

	December 31, 2017
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	193,066	$	—	$	—	$	193,066
U.S. government agencies	—		79,624		—		79,624
Corporate debt securities	—		291,582		—		291,582
Total	$	193,066	$	371,206	$	—	$	564,272
Liabilities:
Derivative liabilities	$	—	$	2,138	$	—	$	2,138
Stock warrant liability	—		—		208		208
Total	$	—	$	2,138	$	208	$	2,346