Investments (Tables)

9 Months Ended

Sep. 30, 2017

Amortized Cost and Fair Value of Available-for-Sale Investments

The amortized cost and fair values of available-for-sale investments are as follows at September 30, 2017 and December 31, 2016 (in thousands):    

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
September 30, 2017
Money market investments	$	16,823	$	—	$	—	$	16,823
Asset-backed securities		3,497		2		5		3,494
Corporate bonds and direct obligations of government agencies		84,885		373		91		85,167
U.S. Treasury obligations		5,496		—		1		5,495
Total	$	110,701	$	375	$	97	$	110,979
December 31, 2016
Money market investments	$	12,395	$	—	$	—	$	12,395
Asset-backed securities		4,027		3		19		4,011
Corporate bonds and direct obligations of government agencies		70,069		150		239		69,980
U.S. Treasury obligations		23,037		2		6		23,033
Total	$	109,528	$	155	$	264	$	109,419

Schedule of Unrealized Loss on Available-for-Sale Investments

For those available-for-sale investments with unrealized losses at September 30, 2017 and December 31, 2016, the following table summarizes the duration of the unrealized loss (in thousands):

	Less than 12 months				12 months or longer						Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
September 30, 2017
Asset-backed securities	$	—	$	—	$	2,311	$	5	$	2,311	$	5
Corporate bonds and direct obligations of government agencies		15,429		21		13,215		70		28,644		91
U.S. Treasury obligations		5,495		1		—		—		5,495		1
Total	$	20,924	$	22	$	15,526	$	75	$	36,450	$	97
December 31, 2016
Asset-backed securities	$	1,363	$	6	$	2,314	$	13	$	3,677	$	19
Corporate bonds and direct obligations of government agencies		28,809		195		1,367		44		30,176		239
U.S. Treasury obligations		12,734		6		—		—		12,734		6
Total	$	42,906	$	207	$	3,681	$	57	$	46,587	$	264