INVESTMENTS IN DEBT SECURITIES - Short-Term and Long-Term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 2,170,182
Fair Value	2,129,888
Short-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	801,257	$ 869,525
Gross Unrealized Gains	28	408
Gross Unrealized Losses	(4,536)	(650)
Fair Value	796,749	869,283
Long-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,368,925	1,536,331
Gross Unrealized Gains	124	111
Gross Unrealized Losses	(35,910)	(10,012)
Fair Value	1,333,139	1,526,430
U.S. agency securities \| Short-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	27,774	73,986
Gross Unrealized Gains	0	150
Gross Unrealized Losses	(117)	(8)
Fair Value	27,657	74,128
U.S. agency securities \| Long-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	148,553	154,454
Gross Unrealized Gains	8	26
Gross Unrealized Losses	(4,463)	(1,160)
Fair Value	144,098	153,320
Corporate bonds \| Short-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	301,285	293,460
Gross Unrealized Gains	22	128
Gross Unrealized Losses	(1,637)	(269)
Fair Value	299,670	293,319
Corporate bonds \| Long-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	581,770	667,699
Gross Unrealized Gains	10	80
Gross Unrealized Losses	(14,881)	(4,572)
Fair Value	566,899	663,207
Commercial paper \| Short-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	13,763	36,088
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	13,763	36,088
Municipal securities \| Short-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,074	5,543
Gross Unrealized Gains	0	5
Gross Unrealized Losses	(39)	0
Fair Value	4,035	5,548
Municipal securities \| Long-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	19,124	22,541
Gross Unrealized Gains	0	2
Gross Unrealized Losses	(606)	(126)
Fair Value	18,518	22,417
Certificates of deposit \| Short-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,495	9,200
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	8,495	9,200
U.S. government securities \| Short-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	425,679	430,992
Gross Unrealized Gains	3	106
Gross Unrealized Losses	(2,589)	(255)
Fair Value	423,093	430,843
U.S. government securities \| Long-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	606,465	678,553
Gross Unrealized Gains	106	3
Gross Unrealized Losses	(15,700)	(4,080)
Fair Value	590,871	674,476
Foreign government securities \| Short-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	20,187	20,256
Gross Unrealized Gains	3	19
Gross Unrealized Losses	(154)	(118)
Fair Value	20,036	20,157
Foreign government securities \| Long-term debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	13,013	13,084
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(260)	(74)
Fair Value	$ 12,753	$ 13,010

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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