Investments (Tables)

3 Months Ended

Mar. 31, 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 March 31, 2015
	Maturity (in years)	Amortized cost	Gross unrealized gains	Gross unrealized losses		Estimated fair value
Corporate debt securities	2 years or less	45,224	2	(9	)	45,217
Commercial paper	1 year or less	8,485	14	—		8,499
		53,709	16	(9	)	53,716

		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