Short-Term Investments (Tables)

3 Months Ended

Mar. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Schedule of Short-Term Investments

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

		As of March 31, 2020
	Maturity	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value
Corporate debt securities	2 years or less	$	228,256	$	162	$	(692	)	$	227,726
Commercial paper	1 year or less	192,594		440		(4		)	193,030
U.S. Agency bonds	2 years or less	44,745		122		—			44,867
U.S. Treasury bills	1 year or less	25,078		154		—			25,232
		$	490,673	$	878	$	(696	)	$	490,855

		As of December 31, 2019
	Maturity	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value
Corporate debt securities	2 years or less	$	160,065	$	233	$	(1	)	$	160,297
Commercial paper	1 year or less	120,862		74		—			120,936
U.S. Agency bonds	2 years or less	50,745		41		(4		)	50,782
U.S. Treasury bills	2 years or less	36,474		27		(1		)	36,500
		$	368,146	$	375	$	(6	)	$	368,515