Investments (Tables)

6 Months Ended

Jun. 30, 2015

Investments, Debt and Equity Securities [Abstract]

Schedule of Available-for-sale Securities Reconciliation

The following tables summarize our short-term investments (dollars in thousands):

		As of June 30, 2015
	Maturity (in years)	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value
Corporate debt securities	1 year or less	$	37,010	$	1	$	(12	)	$	36,999
Commercial paper	1 year or less	8,492		7		—			8,499
		$	45,502	$	8	$	(12	)	$	45,498

		As of December 31, 2014
	Maturity (in years)	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value
Corporate debt securities	1 year or less	$	21,208	$	3	$	(1	)	$	21,210
Commercial paper	1 year or less	1,500		—		—			1,500
		$	22,708	$	3	$	(1	)	$	22,710