Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of Assets Measured at Fair Value on Recurring Basis

Assets measured at fair value on a recurring basis were as follows:

Description	March 31, 2019		Quoted Prices (Unadjusted) in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Money market mutual funds	$	40,291	$	40,291	$	—	$	—
U.S. Treasury securities		69		69		—		—
Total cash equivalents	$	40,360	$	40,360	$	—	$	—
Short-term investments:
Asset-backed securities	$	18,079	$	—	$	18,079	$	—
Commercial paper		56,350		—		56,350		—
Corporate debt securities		45,884		—		45,884		—
U.S. Treasury securities		26,815		—		26,815		—
Total short-term investments	$	147,128	$	—	$	147,128	$	—
Total financial assets	$	187,488	$	40,360	$	147,128	$	—
Description	December 31, 2018		Quoted Prices (Unadjusted) in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Money market mutual funds	$	31,740	$	31,740	$	—	$	—
Commercial paper		5,974		—		5,974		—
U.S. Treasury securities		35		35		—		—
Total cash equivalents	$	37,749	$	31,775	$	5,974	$	—
Short-term investments:
Asset-backed securities	$	19,520	$	—	$	19,520	$	—
Commercial paper		72,597		—		72,597		—
Corporate debt securities		54,461		—		54,461		—
U.S. Treasury securities		29,939		—		29,939		—
Total short-term investments	$	176,517	$	—	$	176,517	$	—
Total financial assets	$	214,266	$	31,775	$	182,491	$	—