Short-term Investments (Tables)

9 Months Ended

Sep. 30, 2015

Investments, Debt and Equity Securities [Abstract]

Short-Term Investments Available-for-Sale Securities

Short-term investments consisted of available-for-sale securities as follows (in thousands):

Type of security as of September 30, 2015	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Corporate debt securities	$	28,300	$	5	$	(9	)	$	28,296
Asset-backed securities		430		—		—			430
Total available-for-sale securities	$	28,730	$	5	$	(9	)	$	28,726

Type of security as of December 31, 2014	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
U.S. government-related debt securities	$	4,502	$	—	$	(4	)	$	4,498
Corporate debt securities		47,345		2		(40	)		47,307
Asset-backed securities		3,198		—		(1	)		3,197
Total available-for-sale securities	$	55,045	$	2	$	(45	)	$	55,002

Fair Values of Available-for-Sale Securities by Contractual Maturity

The fair values of available-for-sale securities by contractual maturity were as follows (in thousands):

Contractual maturity	September 30, 2015		December 31, 2014
Maturing in one year or less	$	28,726	$	51,235
Maturing in one to three years		—		3,767
Total available-for-sale securities	$	28,726	$	55,002

Summary of Investments in Continuous Unrealized Loss Position

The following table summarizes investments that have been in a continuous unrealized loss position as of September 30, 2015 (in thousands):

	Less Than 12 Months					12 Months or Greater					Total
	Fair value		Gross unrealized losses			Fair value		Gross unrealized losses			Fair value		Gross unrealized losses
Corporate debt securities	$	13,275	$	(8	)	$	2,000	$	(1	)	$	15,275	$	(9	)
Total	$	13,275	$	(8	)	$	2,000	$	(1	)	$	15,275	$	(9	)