Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2016

Marketable Securities [Abstract]

Available-for-sale Securities [Table Text Block]

Included in marketable securities as of June 30, 2016 and December 31, 2015 are the following:

June 30, 2016	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market mutual funds	$	17,061	$	—	$	—	$	17,061
Certificates of deposit	5,598		—		—		5,598
Total marketable securities designated as available-for-sale	$	22,659	$	—	$	—	$	22,659

December 31, 2015	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market mutual funds	$	13,244	$	—	$	—	$	13,244
United States treasuries	1,002		—		—		1,002
Corporate notes	2,283		1		—		2,284
Certificates of deposit	6,089		—		—		6,089
Total marketable securities designated as available-for-sale	$	22,618	$	1	$	—	$	22,619

Available-for-sale Securities, Debt Maturities, Amortized Cost And Fair Value Basis [Table Text Block]

The amortized costs and fair value of debt securities as of June 30, 2016 and December 31, 2015 are shown below by effective maturity. Effective maturities may differ from contractual maturities because the issuers of the securities may have the right to prepay obligations without prepayment penalties.

June 30, 2016	Amortized Cost		Fair Value
Due in less than one year	$	4,566	$	4,566
Due after one year and within two years	1,032		1,032
	$	5,598	$	5,598
December 31, 2015	Amortized Cost		Fair Value
Due in less than one year	$	5,515	$	5,516
Due after one year and within two years	3,859		3,859
	$	9,374	$	9,375