Investments (Tables)

9 Months Ended

Sep. 30, 2017

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 September 30, 2017 and December 31, 2016 were as follows (in thousands):

	September 30, 2017
	Amortized		Gross Unrealized		Gross Unrealized			Fair
	Cost		Gains		Losses			Value
Amounts maturing in one year or less
Corporate notes and obligations	$	45,889	$	1	$	(11	)	$	45,879
U.S. government treasury securities		60,454		—		(84	)		60,370
Total short-term available-for-sale debt securities	$	106,343	$	1	$	(95	)	$	106,249

	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