Short-term Investments (Tables)

6 Months Ended

Jun. 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 June 30, 2015	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Corporate debt securities	$	35,419	$	—	$	(29	)	$	35,390
Asset-backed securities		1,394		—		—			1,394
Total available-for-sale securities	$	36,813	$	—	$	(29	)	$	36,784

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	June 30, 2015		December 31, 2014
Maturing in one year or less	$	32,220	$	51,235
Maturing in one to three years		4,564		3,767
Total available-for-sale securities	$	36,784	$	55,002

Summary of Investments in Continuous Unrealized Loss Position for Less Than 12 Months

The following table summarizes investments that have been in a continuous unrealized loss position for less than 12 months and a continuous unrealized loss position for more than 12 months as of June 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	$	26,489	$	(27	)	$	3,002	$	(2	)	$	29,491	$	(29	)
Total	$	26,489	$	(27	)	$	4,395	$	(2	)	$	30,884	$	(29	)