Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2016

Marketable Securities [Abstract]

Amortized Cost And Fair Value Of Marketable Securities

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, 2015		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Corporate bonds	$	177,810	$	24	$	(221)	$	177,613
U.S. government bonds		12,881		-		(10)		12,871
Agency bonds		12,068		-		(3)		12,065
Certificates of deposit		3,500		-		-		3,500
Commercial paper		3,491		-		-		3,491
International government bonds		1,462		-		(3)		1,459
Municipal bonds		1,400		-		(1)		1,399
Treasury bill		1,192		1		-		1,193
Total marketable securities	$	213,804	$	25	$	(238)	$	213,591

Contractual Maturities Of Marketable Securities

As of December 31, 2016		Amortized Cost		Fair Value
Due in one year or less	$	169,044	$	169,002
Due after one through two years		67,951		67,947
	$	236,995	$	236,949