Investments (Tables)

9 Months Ended

Sep. 30, 2017

Investments, Debt and Equity Securities [Abstract]

Schedule of Available-for-sale Securities Reconciliation

The following tables summarize the Company's short-term investments (dollars in thousands):

		As of September 30, 2017
	Maturity	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value
Corporate debt securities	1 year or less	$	26,055	$	—	$	(5	)	$	26,050
Commercial paper	1 year or less	28,130		2		(4		)	28,128
		$	54,185	$	2	$	(9	)	$	54,178

		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