Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Schedule of fair value measurements

The following tables summarize our cash and available-for-sale securities that were measured at fair value by significant category within the fair value hierarchy (in thousands):

	December 31, 2016
	Carrying Amount		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value		Cash and Cash Equivalents		Short-Term Marketable Securities		Long-Term Marketable Securities
Assets:
Cash	$	13,984	$	—	$	—		$	13,984	$	13,984	$	—	$	—
Available-for-sale:
Level I:
Money market funds	21,061		—		—			21,061		21,061		—		—
Level II:
U.S. government and agency securities	24,388		1		(4		)	24,385		—		24,385		—
Total	$	59,433	$	1	$	(4	)	$	59,430	$	35,045	$	24,385	$	—
	December 31, 2015
	Carrying Amount		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value		Cash and Cash Equivalents		Short-Term Marketable Securities		Long-Term Marketable Securities
Assets:
Cash	$	17,889	$	—	$	—		$	17,889	$	17,889	$	—	$	—
Available-for-sale:
Level I:
Money market funds	11,228		—		—			11,228		11,228		—		—
Level II:
U.S. government and agency securities	72,420		—		(72		)	72,348		—		65,855		6,493
Total	$	101,537	$	—	$	(72	)	$	101,465	$	29,117	$	65,855	$	6,493