Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Summary of Company's Cash Equivalents and Marketable Securities

The following tables summarize the Company’s cash equivalents and marketable securities as of March 31, 2021 and December 31, 2020.

	March 31, 2021
	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Cash equivalents	$	899,250	$	816,384	$	82,866	$	—
Total cash equivalents		899,250		816,384		82,866		—
Marketable securities:
U.S. government securities		173,097		—		173,097		—
U.S. corporate bonds		345,857		—		345,857		—
International corporate bonds		202,770		—		202,770		—
U.S. commercial paper		170,796		—		170,796		—
International commercial paper		212,247		—		212,247		—
Total marketable securities		1,104,767		—		1,104,767		—
	$	2,004,017	$	816,384	$	1,187,633	$	—

	December 31, 2020
	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Cash equivalents	$	1,661,082	$	1,637,609	$	23,473	$	—
Total cash equivalents		1,661,082		1,637,609		23,473		—
Marketable securities:
U.S. government securities		160,588		—		160,588		—
U.S. corporate bonds		123,107		—		123,107		—
International corporate bonds		57,676		—		57,676		—
U.S. commercial paper		45,963		—		45,963		—
International commercial paper		51,133		—		51,133		—
Total marketable securities		438,467		—		438,467		—
	$	2,099,549	$	1,637,609	$	461,940	$	—

Summary of Gross Unrealized Gains and Losses of Marketable Securities

The following tables summarize the gross unrealized gains and losses of the Company’s marketable securities as of March 31, 2021 and December 31, 2020:

	March 31, 2021
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Credit Losses		Fair Value
	(in thousands)
Assets:
U.S. government securities	$	173,073	$	30	$	(6	)	$	—	$	173,097
U.S. corporate bonds		346,021		118		(282	)		—		345,857
International corporate bonds		202,848		70		(148	)		—		202,770
U.S. commercial paper		170,803		4		(11	)		—		170,796
International commercial paper		212,258		—		(11	)		—		212,247
	$	1,105,003	$	222	$	(458	)	$	—	$	1,104,767

	December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Credit Losses		Fair Value
	(in thousands)
Assets:
U.S. government securities	$	160,589	$	11	$	(12	)	$	—	$	160,588
U.S. corporate bonds		122,882		240		(15	)		—		123,107
International corporate bonds		57,485		200		(9	)		—		57,676
U.S. commercial paper		45,963		—		—			—		45,963
International commercial paper		51,133		—		—			—		51,133
	$	438,052	$	451	$	(36	)	$	—	$	438,467