Marketable Securities

6 Months Ended

Jun. 30, 2019

Cash And Cash Equivalents [Abstract]

Marketable Securities

3. Marketable Securities

The following tables summarize the amortized cost, gross unrealized gains and losses and fair value of our short-term and long-term investments as of June 30, 2019 and December 31, 2018 (in thousands):

	June 30, 2019
			Gross		Gross
	Amortized		Unrealized		Unrealized		Aggregate
	Cost		Gains		Losses		Fair Value
Short-term investments:
Corporate debt securities	$	134,219	$	43	$	—	$	134,262
U.S. government and government agency debt    securities		3,000		3		—		3,003
Total	$	137,219	$	46	$	—	$	137,265
Long-term investments:
Corporate debt securities	$	1,997	$	7			$	2,004
Total	$	1,997	$	7	$	—	$	2,004

	December 31, 2018
			Gross		Gross
	Amortized		Unrealized		Unrealized		Aggregate
	Cost		Gains		Losses		Fair Value
Short-term investments:
Corporate debt securities	$	36,230	$	2	$	—	$	36,232
Total	$	36,230	$	2	$	—	$	36,232

As of June 30, 2019, all of our short-term investments have contractual maturities of one year or less and all of our long-term investments have contractual maturities between one and two years.  

As of June 30, 2019, we did not consider any of our short-term or long-term investments to be other-than-temporarily impaired. We do not intend to sell, nor do we believe it is more likely than not that we will be required to sell, any of the securities in an unrealized loss position. When evaluating our investments for other-than-temporary impairment, we review factors such as the length of time and extent to which fair value has been below its cost basis, the financial condition of the issuer, our ability and intent to hold the security to maturity and whether it is more likely than not that we will be required to sell the investment before recovery of the amortized cost basis.