Investments (Tables)

12 Months Ended

Dec. 31, 2016

Available For Sale Securities [Abstract]

Amortized Cost and Fair Value on Available-for-Sale Investments and Unrealized Gains and Losses

The amortized cost and fair value on the available-for-sale investments and unrealized gains and losses as of December 31, 2016 and 2015 were as follows (in thousands):

	December 31, 2016
	Amortized		Gross Unrealized		Gross Unrealized			Fair
	Cost		Gains		Losses			Value
Amounts maturing in one year or less
Corporate notes and obligations	$	29,866	$	—	$	(25	)	$	29,841
U.S. government treasury securities		6,900		—		—			6,900
Total short-term available-for-sale debt securities	$	36,766	$	—	$	(25	)	$	36,741
Amounts maturing in greater than one year
Corporate notes and obligations	$	4,010	$	—	$	(11	)	$	3,999
U.S. government treasury securities		34,505		—		(58	)		34,447
Total long-term available-for-sale debt securities	$	38,515	$	—	$	(69	)	$	38,446

	December 31, 2015
	Amortized		Gross Unrealized		Gross Unrealized			Fair
	Cost		Gains		Losses			Value
Amounts maturing in one year or less
Corporate notes and obligations	$	2,245	$	—	$	—		$	2,245
U.S. agency securities		3,016		—		(1	)		3,015
U.S. government treasury securities		999		1		—			1,000
Total available-for-sale debt securities	$	6,260	$	1	$	(1	)	$	6,260