Investments In Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2019

Investments Debt And Equity Securities [Abstract]

Summary of Cost, Gross Unrealized Holding Gains and Losses and Fair Value of Available-for-sale Investments by Types and Classes of Security

The cost, gross unrealized holding gains, gross unrealized holding losses and fair value of available-for-sale investments by types and classes of security at June 30, 2019 consisted of the following (in thousands):

		June 30, 2019
	Maturity (in years)	Amortized Cost Basis		Other-than- temporary Impairments		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
Commercial paper	1 year or less	$	97,704	$	—	$	155	$	—	$	97,859
Corporate debt securities	1 year or less		34,712		—		68		—		34,780
Government-sponsored enterprise securities	1 year or less		9,000		—		5		—		9,005
Total available-for-sale securities		$	141,416	$	—	$	228	$	—	$	141,644