MARKETABLE SECURITIES (Composition of Marketable Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	$ 140,383	$ 157,247
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	480,419	430,996
Commercial Paper [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	36,209	38,253
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	106,720	140,651
U.S. Government And Agency Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	26,655	45,706
Short-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	244,577	249,895
Gross Unrealized Gains	77	593
Gross Unrealized Losses	(1,149)	(110)
Fair Value	243,505	250,378
Short-term Investments [Member] \| Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	41,252	66,379
Gross Unrealized Gains	9	99
Gross Unrealized Losses	(110)	(11)
Fair Value	41,151	66,467
Short-term Investments [Member] \| Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	147,401	107,102
Gross Unrealized Gains	57	434
Gross Unrealized Losses	(927)	(65)
Fair Value	146,531	107,471
Short-term Investments [Member] \| Commercial Paper [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	36,251	38,252
Gross Unrealized Gains		2
Gross Unrealized Losses	(42)	(1)
Fair Value	36,209	38,253
Short-term Investments [Member] \| Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	6,603	12,931
Gross Unrealized Gains	11	58
Fair Value	6,614	12,989
Short-term Investments [Member] \| U.S. Government And Agency Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	13,070	25,231
Gross Unrealized Losses	(70)	(33)
Fair Value	13,000	25,198
Long-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	558,782	564,355
Gross Unrealized Gains	99	456
Gross Unrealized Losses	(12,000)	(2,336)
Fair Value	546,881	562,475
Long-term Investments [Member] \| Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	101,483	91,185
Gross Unrealized Gains	4	4
Gross Unrealized Losses	(2,255)	(409)
Fair Value	99,232	90,780
Long-term Investments [Member] \| Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	341,254	324,492
Gross Unrealized Gains	76	351
Gross Unrealized Losses	(7,442)	(1,318)
Fair Value	333,888	323,525
Long-term Investments [Member] \| Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	102,013	128,139
Gross Unrealized Gains	19	101
Gross Unrealized Losses	(1,926)	(578)
Fair Value	100,106	127,662
Long-term Investments [Member] \| U.S. Government And Agency Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	14,032	20,539
Gross Unrealized Losses	(377)	(31)
Fair Value	$ 13,655	$ 20,508

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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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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