Fair Value Measurement (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Summary of Fair Value Measurements of Cash Equivalents, and Available-for-Sale Marketable Securities

The fair value measurements of the Company’s cash equivalents and available-for-sale marketable securities are identified at the following levels within the fair value hierarchy (in thousands):

	March 31, 2018
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	20,142	$	20,142	$	—	$	—
Total		20,142		20,142		—		—
Marketable securities:
Commercial paper securities		125,881		—		125,881		—
Corporate debt securities		74,923		—		74,923		—
U.S. government-sponsored entity debt securities		3,000		—		3,000		—
Total		203,804		—		203,804		—
Total cash equivalents and marketable securities	$	223,946	$	20,142	$	203,804		—

	December 31, 2017
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	24,290	$	24,290	$	—	$	—
Commercial paper securities		4,595		—		4,595		—
Total		28,885		24,290		4,595		—
Marketable securities:
Commercial paper securities		110,247		—		110,247		—
Corporate debt securities		75,755		—		75,755		—
U.S. government-sponsored entity debt securities		8,492		—		8,492		—
Total		194,494		—		194,494		—
Total cash equivalents and marketable securities	$	223,379	$	24,290	$	199,089		—