Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value Measurements of Cash Equivalents, Available-For-Sale Investment Securities and Equity Securities

The recurring fair value measurements of the Company’s cash equivalents, available-for-sale investment securities and equity securities at March 31, 2020 and December 31, 2019 consisted of the following (in thousands):

			Fair Value Measurements at Reporting Date Using
	March 31, 2020		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market fund	$	139,886	$	139,886	$	—	$	—
U.S. Treasury notes		251,128		251,128		—		—
Equity securities		810		810		—		—
Government sponsored enterprise securities		71,322		—		71,322		—
Corporate debt securities		111,658		—		111,658		—
Commercial paper		55,238		—		55,238		—
	$	630,042	$	391,824	$	238,218	$	—

			Fair Value Measurements at Reporting Date Using
	December 31, 2019		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market fund	$	98,084	$	98,084	$	—	$	—
U.S. Treasury notes		228,603		228,603		—		—
Equity securities		2,307		2,307		—		—
Government sponsored enterprise securities		103,878		—		103,878		—
Corporate debt securities		88,039		—		88,039		—
Commercial paper		102,212		—		102,212		—
	$	623,123	$	328,994	$	294,129	$	—