INVESTMENTS IN DEBT SECURITIES - Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Short-term debt securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	$ 699,479	$ 628,655
Less than 12 Months, Gross Unrealized Losses	(4,536)	(650)
Greater than 12 months, Fair Value	0	311
Greater than 12 months, Gross Unrealized Losses	0	0
Total, Fair Value	699,479	628,966
Total, Gross Unrealized Losses	(4,536)	(650)
Short-term debt securities \| U.S. agency securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	27,657	26,749
Less than 12 Months, Gross Unrealized Losses	(117)	(8)
Greater than 12 months, Fair Value	0	0
Greater than 12 months, Gross Unrealized Losses	0	0
Total, Fair Value	27,657	26,749
Total, Gross Unrealized Losses	(117)	(8)
Short-term debt securities \| Corporate bonds
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	259,332	241,792
Less than 12 Months, Gross Unrealized Losses	(1,637)	(269)
Greater than 12 months, Fair Value	0	311
Greater than 12 months, Gross Unrealized Losses	0	0
Total, Fair Value	259,332	242,103
Total, Gross Unrealized Losses	(1,637)	(269)
Short-term debt securities \| Municipal securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	3,267
Less than 12 Months, Gross Unrealized Losses	(39)
Greater than 12 months, Fair Value	0
Greater than 12 months, Gross Unrealized Losses	0
Total, Fair Value	3,267
Total, Gross Unrealized Losses	(39)
Short-term debt securities \| U.S. government securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	390,493	347,380
Less than 12 Months, Gross Unrealized Losses	(2,589)	(255)
Greater than 12 months, Fair Value	0	0
Greater than 12 months, Gross Unrealized Losses	0	0
Total, Fair Value	390,493	347,380
Total, Gross Unrealized Losses	(2,589)	(255)
Short-term debt securities \| Foreign government securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	18,730	12,734
Less than 12 Months, Gross Unrealized Losses	(154)	(118)
Greater than 12 months, Fair Value	0	0
Greater than 12 months, Gross Unrealized Losses	0	0
Total, Fair Value	18,730	12,734
Total, Gross Unrealized Losses	(154)	(118)
Long-term debt securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	1,202,420	1,450,038
Less than 12 Months, Gross Unrealized Losses	(35,261)	(10,012)
Greater than 12 months, Fair Value	21,599	0
Greater than 12 months, Gross Unrealized Losses	(649)	0
Total, Fair Value	1,224,019	1,450,038
Total, Gross Unrealized Losses	(35,910)	(10,012)
Long-term debt securities \| U.S. agency securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	138,033	151,472
Less than 12 Months, Gross Unrealized Losses	(4,295)	(1,160)
Greater than 12 months, Fair Value	4,832	0
Greater than 12 months, Gross Unrealized Losses	(168)	0
Total, Fair Value	142,865	151,472
Total, Gross Unrealized Losses	(4,463)	(1,160)
Long-term debt securities \| Corporate bonds
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	545,068	627,467
Less than 12 Months, Gross Unrealized Losses	(14,400)	(4,572)
Greater than 12 months, Fair Value	16,767	0
Greater than 12 months, Gross Unrealized Losses	(481)	0
Total, Fair Value	561,835	627,467
Total, Gross Unrealized Losses	(14,881)	(4,572)
Long-term debt securities \| Municipal securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	15,418	18,616
Less than 12 Months, Gross Unrealized Losses	(606)	(126)
Greater than 12 months, Fair Value	0	0
Greater than 12 months, Gross Unrealized Losses	0	0
Total, Fair Value	15,418	18,616
Total, Gross Unrealized Losses	(606)	(126)
Long-term debt securities \| U.S. government securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	491,148	639,473
Less than 12 Months, Gross Unrealized Losses	(15,700)	(4,080)
Greater than 12 months, Fair Value	0	0
Greater than 12 months, Gross Unrealized Losses	0	0
Total, Fair Value	491,148	639,473
Total, Gross Unrealized Losses	(15,700)	(4,080)
Long-term debt securities \| Foreign government securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Less than 12 Months, Fair Value	12,753	13,010
Less than 12 Months, Gross Unrealized Losses	(260)	(74)
Greater than 12 months, Fair Value	0	0
Greater than 12 months, Gross Unrealized Losses	0	0
Total, Fair Value	12,753	13,010
Total, Gross Unrealized Losses	$ (260)	$ (74)

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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