Marketable Securities

12 Months Ended

Dec. 31, 2017

NOTE 5. MARKETABLE SECURITIES

During the year ended December 31, 2017, we purchased marketable debt securities, which are classified as available-for-sale and carried at fair value in the accompanying consolidated balance sheets on a trade date basis. We have classified our investments with maturities beyond one year as short-term, based on their highly liquid nature and because such marketable securities represent the investment of cash that is available for current operations. Unrealized holding gains and losses are deferred within accumulated other comprehensive income (“AOCI”), net of applicable taxes, except when an impairment is determined to be other-than-temporary or the security is divested prior to maturity. Within the accompanying consolidated statements of operations, interest earned and amortization of premiums or discounts on marketable securities are included in interest income, and realized gains and losses on the sale of our marketable securities are included in other income.

The amortized cost and fair value of marketable securities were as follows (in thousands):


As of December 31, 2017		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value

Corporate bonds	$	140,969	$	96	$	(179)	$	140,886
Certificates of deposit		58,510		-		-		58,510
Commercial paper		29,171		-		-		29,171
Asset backed securities		22,206		4		(43)		22,167
U.S. government bonds		15,619		11		(19)		15,611
Agency bonds		10,990		9		(52)		10,947
Treasury bills		6,964		-		(1)		6,963
Total marketable securities	$	284,429	$	120	$	(294)	$	284,255

As of December 31, 2016		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value

Corporate bonds	$	130,833	$	40	$	(102)	$	130,771
Certificates of deposit		40,400		-		-		40,400
Asset backed securities		27,290		25		-		27,315
Commercial paper		20,228		-		-		20,228
U.S. government bonds		12,244		1		(14)		12,231
Agency bonds		4,600		4		-		4,604
Municipal bonds		1,400		-		-		1,400
Total marketable securities	$	236,995	$	70	$	(116)	$	236,949

As of December 31, 2017, unrealized losses on marketable securities that have been in a continuous loss position for more than twelve months were not material. Our portfolio of marketable securities had an average AA- credit rating as of December 31, 2017. There were no marketable securities that we consider to be other-than-temporarily impaired as of December 31, 2017. Our investment strategy is to buy short-duration marketable securities with a high credit rating. Some of our marketable securities have call features that can effectively shorten the lifespan from the contractual maturity date. We use effective maturity date to measure the duration of the marketable securities.

Remaining effective maturities of marketable securities were as follows (in thousands):


As of December 31, 2017		Amortized Cost		Fair Value

Due in one year or less	$	175,849	$	175,780
Due after one through three years		108,580		108,475
	$	284,429	$	284,255