Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Schedule of Fair Value Assets Measured on Recurring Basis

The following table presents the balances of assets measured at fair value on a recurring basis as of December 31, 2017 and 2016:

	December 31, 2017		December 31, 2016
	Level 2		Level 2
	(in thousands)
Money market funds	$	93	$	1,723
Commercial paper		61,317		131,937
Corporate bonds		3,374		16,089
U.S. government agency bonds		—		5,500
Total	$	64,784	$	155,249