Cash Equivalents and Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2017

Investments Debt And Equity Securities [Abstract]

Schedule of Estimated Fair Value of Cash Equivalents and Marketable Securities

The following tables summarize the estimated fair value of our cash equivalents and marketable securities and the gross unrealized gains and losses (in thousands):

	December 31, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Cash equivalents:
Money market funds	$	1,674	$	—	$	—		$	1,674
Reverse repurchase agreements		7,250		—		—			7,250
Total cash equivalents		8,924		—		—			8,924
Marketable securities:
U.S. treasury securities		1,502		—		(1	)		1,501
U.S. government securities		36,082		—		(101	)		35,981
Total marketable securities	$	37,584	$	—	$	(102	)	$	37,482

	December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Cash equivalents:
Money market funds	$	4,584	$	—	$	—		$	4,584
Reverse repurchase agreements		39,250		—		—			39,250
Total cash equivalents		43,834		—		—			43,834
Marketable securities:
U.S. government securities		15,758		—		(4	)		15,754
Total marketable securities	$	15,758	$	—	$	(4	)	$	15,754

Summary of Contractual Maturities of Marketable Securities at Estimated Fair Value

The following table summarizes the contractual maturities of the Company's marketable securities at estimated fair value (in thousands):

	December 31,
	2017		2016
Due in one year or less	$	34,498	$	15,754
Due in 1 - 2 years		2,984		—
Total marketable securities	$	37,482	$	15,754