Marketable Securities and Equity Investments (Tables)

12 Months Ended

Dec. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Summary of Cash, Cash Equivalents and Marketable Securities

A summary of the Company’s cash equivalents and marketable securities, which are recorded at fair value (and do not include $2.8 billion and $2.3 billion of cash as of December 31, 2020 and 2019, respectively), is shown below:

	As of December 31, 2020								As of December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(in thousands)
Cash equivalents:
Money market funds	$	3,141,053	$	—	$	—	$	3,141,053	$	791,039	$	—	$	—	$	791,039
Corporate debt securities	—		—		—		—		6,070		—		—		6,070
Commercial paper	—		—		—		—		29,470		3		(1)		29,472
Total cash equivalents	$	3,141,053	$	—	$	—	$	3,141,053	$	826,579	$	3	$	(1)	$	826,581
Marketable securities:
Government-sponsored enterprise securities	$	80,046	$	17	$	—	$	80,063	$	12,689	$	44	$	—	$	12,733
Corporate debt securities	231,263		377		(42)		231,598		301,458		391		(50)		301,799
Commercial paper	163,286		19		(37)		163,268		102,240		121		(5)		102,356
Total marketable debt securities	474,595		413		(79)		474,929		416,387		556		(55)		416,888
Corporate equity securities	51,427		144,354		—		195,781		113,829		168,255		—		282,084
Total marketable securities	$	526,022	$	144,767	$	(79)	$	670,710	$	530,216	$	168,811	$	(55)	$	698,972

Available-for-sale debt securities were classified on the Company’s consolidated balance sheets as follows at fair value:

	December 31,
	2020		2019
	(in thousands)
Cash and cash equivalents	$	3,141,053	$	826,581
Marketable securities	474,929		416,888
Total	$	3,615,982	$	1,243,469

Available-for-sale debt securities by contractual maturity were as follows:

	December 31,
	2020		2019
	(in thousands)
Matures within one year	$	3,526,185	$	1,137,942
Matures after one year through five years	89,797		105,527
Total	$	3,615,982	$	1,243,469

Schedule of Company’s Net Unrealized Gains on Corporate Equity Securities

During the three years ended December 31, 2020, the Company’s net unrealized gains on corporate equity securities held at the conclusion of each period were as follows:

	2020		2019		2018
	(in thousands)
Net unrealized gains	$	136,167	$	143,175	$	2,558

Schedule of Sale of Equity Investments

During the years ended December 31, 2020 and 2019, the Company sold the common stock of publicly traded companies, which were primarily sales of its investment in CRISPR, resulting in the following:

	2020		2019
	(in thousands)
Proceeds received	$	437,567	$	94,936
Weighted-average cost basis	$	103,332	$	29,825