Marketable Securities

12 Months Ended

Dec. 31, 2017

Investments Debt And Equity Securities [Abstract]

Marketable Securities

4. Marketable Securities

The following table summarizes the available-for-sale securities held at December 31, 2017 and 2016 (in thousands):

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2017
Description:
U.S. government agency securities and treasuries	$	—	$	—	$	—		$	—
Total	$	—	$	—	$	—		$	—
December 31, 2016
Description:
U.S. government agency securities and treasuries	$	79,411	$	—	$	(9	)	$	79,402
Total	$	79,411	$	—	$	(9	)	$	79,402

The estimated market value of marketable securities by maturity date is as follows (in thousands):

	December 31,
	2017		2016
Due in one year or less	$	—	$	79,402
Total	$	—	$	79,402

The amortized cost of available-for-sale securities is adjusted for amortization of premiums and accretion of discounts to maturity. There were no realized gains or losses recognized during the years ended December 31, 2017 and 2016, and as a result, the Company did not reclassify any amount out of accumulated other comprehensive loss for the same period.