Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2018

Investments Disclosure [Abstract]

Summary of Investments Included in Cash Equivalents and Short Term Investments

The following table summarizes the Company’s investments, which are included in cash equivalents and short-term investments:

December 31, 2018	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Money market mutual funds	$	31,740	$	—	$	—		$	31,740
Asset-backed securities		19,541		—		(21	)		19,520
Commercial paper		78,571		—		—			78,571
Corporate debt securities		54,511		—		(50	)		54,461
U.S. Treasury securities		29,980		—		(6	)		29,974
Total	$	214,343	$	—	$	(77	)	$	214,266
December 31, 2017	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Money market mutual funds	$	44,182	$	—	$	—		$	44,182
Asset-backed securities		7,428		—		(6	)		7,422
Commercial paper		34,882		—		—			34,882
Corporate debt securities		26,906		—		(50	)		26,856
U.S. Treasury securities		8,941		—		(17	)		8,924
Total	$	122,339	$	—	$	(73	)	$	122,266