Short-term Investments (Tables)

6 Months Ended

Jun. 30, 2019

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 June 30, 2019
	Maturity	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value
Corporate debt securities	2 years or less	$	116,958	$	156	$	(5	)	$	117,109
Commercial paper	1 year or less	89,293		93		—			89,386
U.S. Treasury bills	1 year or less	18,921		25		—			18,946
U.S. Agency bonds	2 years or less	6,000		—		(2		)	5,998
Other sovereign securities	1 year or less	1,995		1		—			1,996
		$	233,167	$	275	$	(7	)	$	233,435

		As of December 31, 2018
	Maturity	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value
Corporate debt securities	1 year or less	$	111,933	$	26	$	(43	)	$	111,916
Commercial paper	1 year or less	74,433		—		(24		)	74,409
U.S. Treasury bills	1 year or less	3,771		—		—			3,771
		$	190,137	$	26	$	(67	)	$	190,096