Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2017

Marketable Securities [Abstract]

Amortized Cost And Fair Value Of Marketable Securities

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

Contractual Maturities Of Marketable Securities

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