Marketable Securities and Equity Investments - Summary of Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2020	Dec. 31, 2019
Total marketable debt securities
Fair Value	$ 2,974,765	$ 1,243,469
Corporate equity securities
Amortized Cost	67,054	113,829
Gross Unrealized Gains	152,273	168,255
Gross Unrealized Losses	0	0
Fair Value	219,327	282,084
Amortized Cost	464,733	530,216
Gross Unrealized Gains	154,717	168,811
Gross Unrealized Losses	(13)	(55)
Fair Value	619,437	698,972
Cash equivalents
Total marketable debt securities
Amortized Cost	2,574,633	826,579
Gross Unrealized Gains	23	3
Gross Unrealized Losses	(1)	(1)
Fair Value	2,574,655	826,581
Cash equivalents \| Money market funds
Total marketable debt securities
Amortized Cost	2,476,713	791,039
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	2,476,713	791,039
Cash equivalents \| Commercial paper
Total marketable debt securities
Amortized Cost	93,084	29,470
Gross Unrealized Gains	23	3
Gross Unrealized Losses	0	(1)
Fair Value	93,107	29,472
Cash equivalents \| Corporate debt securities
Total marketable debt securities
Amortized Cost	4,836	6,070
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	0
Fair Value	4,835	6,070
Marketable securities
Total marketable debt securities
Amortized Cost	397,679	416,387
Gross Unrealized Gains	2,444	556
Gross Unrealized Losses	(13)	(55)
Fair Value	400,110	416,888
Marketable securities \| Government-sponsored enterprise securities
Total marketable debt securities
Amortized Cost	11,198	12,689
Gross Unrealized Gains	55	44
Gross Unrealized Losses	0	0
Fair Value	11,253	12,733
Marketable securities \| Corporate debt securities
Total marketable debt securities
Amortized Cost	292,085	301,458
Gross Unrealized Gains	1,897	391
Gross Unrealized Losses	(6)	(50)
Fair Value	293,976	301,799
Marketable securities \| Commercial paper
Total marketable debt securities
Amortized Cost	94,396	102,240
Gross Unrealized Gains	492	121
Gross Unrealized Losses	(7)	(5)
Fair Value	$ 94,881	$ 102,356

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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