Marketable Securities

6 Months Ended

Jun. 30, 2017

Note 5. marketable securities

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


As of June 30, 2017		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value

Corporate bonds	$	131,017	$	128	$	(32)	$	131,113
Certificates of deposit		44,423		-		-		44,423
Asset backed securities		29,890		9		(10)		29,889
Commercial paper		14,816		-		-		14,816
U.S. government bonds		21,093		8		(14)		21,087
Treasury bills		7,986		-		-		7,986
Agency bonds		7,599		13		(3)		7,609
Total marketable securities	$	256,824	$	158	$	(59)	$	256,923

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 June 30, 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 June 30, 2017. There were no marketable securities that we consider to be other-than-temporarily impaired as of June 30, 2017.

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


As of June 30, 2017		Amortized Cost		Fair Value

Due in one year or less	$	162,639	$	162,646
Due after one year through three years		94,185		94,277
	$	256,824	$	256,923

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 the effective maturity date to measure the duration of the marketable securities.