Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Summary of Assets Measured at Fair Value on Recurring Basis

The following tables present the balances of assets measured at fair value on a recurring basis, by level within the fair value hierarchy, as of the date presented (in thousands):

	March 31, 2018
	LEVEL 1		LEVEL 2
Cash equivalents:
Money market funds	$	13,772	$	—
Commercial paper		—		2,997
Treasury bill		—		2,500
Short-term investments:
U.S. government agency securities		—		9,937
Corporate notes and bonds		—		7,540
Commercial paper		—		3,983
Treasury bill		—		8,413
Total	$	13,772	$	35,370

	December 31, 2017
	LEVEL 1		LEVEL 2
Cash equivalents:
Money market funds	$	10,393	$	—
Commercial paper		—		1,000
Short-term investments:
U.S. government agency securities		—		13,970
Corporate notes and bonds		—		7,503
Commercial paper		—		8,972
Treasury bills		—		8,386
Total	$	10,393	$	39,831