Investments (Tables)

6 Months Ended

Jun. 30, 2017

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, 2017
	Maturity	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value
Corporate debt securities	1 year or less	$	31,306	$	—	$	(16	)	$	31,290
Commercial paper	2 years or less	36,597		2		(6		)	36,593
		$	67,903	$	2	$	(22	)	$	67,883

		As of December 31, 2016
	Maturity	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value
Corporate debt securities	1 year or less	$	20,622	$	—	$	(3	)	$	20,619
Commercial paper	1 year or less	13,717		15		—			13,732
		$	34,339	$	15	$	(3	)	$	34,351