Marketable Securities

9 Months Ended

Sep. 30, 2017

Investments Debt And Equity Securities [Abstract]

2. Marketable Securities

The following table summarizes our amortized cost, gross unrealized gains and losses, and fair value of our available-for-sale marketable securities as of September 30, 2017 (in thousands):

	September 30, 2017
			Gross		Gross
	Amortized		Unrealized		Unrealized			Aggregate
	Cost		Gains		Losses			Fair Value
Corporate debt securities		255,002		—		(30	)		254,972
Total	$	255,002	$	—	$	(30	)	$	254,972

All of our available-for-sale marketable securities have contractual maturities of one year or less as of September 30, 2017. We had no short-term and long-term marketable securities as of December 31, 2016.

Changes in market interest rates and bond yields caused certain investments to fall below their cost basis, resulting in unrealized losses on marketable securities. None of these securities were in a material continuous unrealized loss position for more than 12 months.

As of September 30, 2017, we did not consider any of our marketable securities 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.