FAIR VALUE MEASUREMENTS - Schedule of Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair value measurements
Cash, cash equivalents, and restricted cash	$ 274,076	$ 1,491,594
Estimated Fair Value	941,620	937,172
Equity securities	3,068	1,521
Restricted cash
Fair value measurements
Cash, cash equivalents, and restricted cash	297	306
Fair Value, Recurring
Fair value measurements
Equity securities	3,068	1,521
Non-marketable securities	2,540
Contingent consideration	(363,647)	(2,477)
Total	857,657	1,837,816
Fair Value, Recurring \| Corporate bonds
Fair value measurements
Estimated Fair Value	368,832	132,913
Fair Value, Recurring \| Certificates of deposit
Fair value measurements
Estimated Fair Value	175,542
Fair Value, Recurring \| Commercial paper
Fair value measurements
Estimated Fair Value	10,001
Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Estimated Fair Value	276,081	207,171
Fair Value, Recurring \| Asset backed securities
Fair value measurements
Estimated Fair Value	111,164	7,094
Fair Value, Recurring \| Cash and money market
Fair value measurements
Cash, cash equivalents, and restricted cash	273,779	901,294
Fair Value, Recurring \| Restricted cash
Fair value measurements
Cash, cash equivalents, and restricted cash	297	306
Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Cash, cash equivalents, and restricted cash		589,994
Level 1 \| Fair Value, Recurring
Fair value measurements
Equity securities	0	1,521
Non-marketable securities	0
Contingent consideration	0	0
Total	274,076	903,121
Level 1 \| Fair Value, Recurring \| Corporate bonds
Fair value measurements
Estimated Fair Value	0	0
Level 1 \| Fair Value, Recurring \| Certificates of deposit
Fair value measurements
Estimated Fair Value	0
Level 1 \| Fair Value, Recurring \| Commercial paper
Fair value measurements
Estimated Fair Value	0
Level 1 \| Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Estimated Fair Value	0	0
Level 1 \| Fair Value, Recurring \| Asset backed securities
Fair value measurements
Estimated Fair Value	0	0
Level 1 \| Fair Value, Recurring \| Cash and money market
Fair value measurements
Cash, cash equivalents, and restricted cash	273,779	901,294
Level 1 \| Fair Value, Recurring \| Restricted cash
Fair value measurements
Cash, cash equivalents, and restricted cash	297	306
Level 1 \| Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Cash, cash equivalents, and restricted cash		0
Level 2 \| Fair Value, Recurring
Fair value measurements
Equity securities	3,068	0
Non-marketable securities	0
Contingent consideration	0	0
Total	944,688	937,172
Level 2 \| Fair Value, Recurring \| Corporate bonds
Fair value measurements
Estimated Fair Value	368,832	132,913
Level 2 \| Fair Value, Recurring \| Certificates of deposit
Fair value measurements
Estimated Fair Value	175,542
Level 2 \| Fair Value, Recurring \| Commercial paper
Fair value measurements
Estimated Fair Value	10,001
Level 2 \| Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Estimated Fair Value	276,081	207,171
Level 2 \| Fair Value, Recurring \| Asset backed securities
Fair value measurements
Estimated Fair Value	111,164	7,094
Level 2 \| Fair Value, Recurring \| Cash and money market
Fair value measurements
Cash, cash equivalents, and restricted cash	0	0
Level 2 \| Fair Value, Recurring \| Restricted cash
Fair value measurements
Cash, cash equivalents, and restricted cash	0	0
Level 2 \| Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Cash, cash equivalents, and restricted cash		589,994
Level 3 \| Fair Value, Recurring
Fair value measurements
Equity securities	0	0
Non-marketable securities	2,540
Contingent consideration	(363,647)	(2,477)
Total	(361,107)	(2,477)
Level 3 \| Fair Value, Recurring \| Corporate bonds
Fair value measurements
Estimated Fair Value	0	0
Level 3 \| Fair Value, Recurring \| Certificates of deposit
Fair value measurements
Estimated Fair Value	0
Level 3 \| Fair Value, Recurring \| Commercial paper
Fair value measurements
Estimated Fair Value	0
Level 3 \| Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Estimated Fair Value	0	0
Level 3 \| Fair Value, Recurring \| Asset backed securities
Fair value measurements
Estimated Fair Value	0	0
Level 3 \| Fair Value, Recurring \| Cash and money market
Fair value measurements
Cash, cash equivalents, and restricted cash	0	0
Level 3 \| Fair Value, Recurring \| Restricted cash
Fair value measurements
Cash, cash equivalents, and restricted cash	$ 0	0
Level 3 \| Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Cash, cash equivalents, and restricted cash		$ 0

Amount of 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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Amount of liability recognized arising from contingent consideration in a business combination, expected to be settled within one year or the normal operating cycle, if longer.

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