MARKETABLE SECURITIES (Composition of Marketable Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Short-term	$ 260,125
Gross Unrealized Losses, Short-term	(2,887)
Fair Value, Short-term	257,238
Amortized Cost, Long-term	490,361
Gross Unrealized Gains, Long-term	47
Gross Unrealized Losses, Long-term	(16,745)
Fair Value, Long-term	473,663
Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Short-term	54,222
Gross Unrealized Losses, Short-term	(563)
Fair Value, Short-term	53,659
Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Long-term	78,945
Gross Unrealized Gains, Long-term	36
Gross Unrealized Losses, Long-term	(2,376)
Fair Value, Long-term	76,605
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Short-term	161,078
Gross Unrealized Losses, Short-term	(2,204)
Fair Value, Short-term	158,874
Amortized Cost, Long-term	296,821
Gross Unrealized Gains, Long-term	1
Gross Unrealized Losses, Long-term	(11,450)
Fair Value, Long-term	285,372
Commercial Paper [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Short-term	25,790
Gross Unrealized Losses, Short-term	(23)
Fair Value, Short-term	25,767
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Short-term	6,000
Fair Value, Short-term	6,000
Amortized Cost, Long-term	95,929
Gross Unrealized Gains, Long-term	10
Gross Unrealized Losses, Long-term	(2,461)
Fair Value, Long-term	93,478
U.S. Government And Agency Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Short-term	13,035
Gross Unrealized Losses, Short-term	(97)
Fair Value, Short-term	12,938
Amortized Cost, Long-term	18,666
Gross Unrealized Losses, Long-term	(458)
Fair Value, Long-term	$ 18,208
Short-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Short-term		$ 249,895
Gross Unrealized Gains, Short-term		593
Gross Unrealized Losses, Short-term		(110)
Fair Value, Short-term		250,378
Short-term Investments [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Short-term		66,379
Gross Unrealized Gains, Short-term		99
Gross Unrealized Losses, Short-term		(11)
Fair Value, Short-term		66,467
Short-term Investments [Member] | Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Short-term		107,102
Gross Unrealized Gains, Short-term		434
Gross Unrealized Losses, Short-term		(65)
Fair Value, Short-term		107,471
Short-term Investments [Member] | Commercial Paper [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Short-term		38,252
Gross Unrealized Gains, Short-term		2
Gross Unrealized Losses, Short-term		(1)
Fair Value, Short-term		38,253
Short-term Investments [Member] | Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Short-term		12,931
Gross Unrealized Gains, Short-term		58
Fair Value, Short-term		12,989
Short-term Investments [Member] | U.S. Government And Agency Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Short-term		25,231
Gross Unrealized Losses, Short-term		(33)
Fair Value, Short-term		25,198
Long-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Long-term		564,355
Gross Unrealized Gains, Long-term		456
Gross Unrealized Losses, Long-term		(2,336)
Fair Value, Long-term		562,475
Long-term Investments [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Long-term		91,185
Gross Unrealized Gains, Long-term		4
Gross Unrealized Losses, Long-term		(409)
Fair Value, Long-term		90,780
Long-term Investments [Member] | Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Long-term		324,492
Gross Unrealized Gains, Long-term		351
Gross Unrealized Losses, Long-term		(1,318)
Fair Value, Long-term		323,525
Long-term Investments [Member] | Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Long-term		128,139
Gross Unrealized Gains, Long-term		101
Gross Unrealized Losses, Long-term		(578)
Fair Value, Long-term		127,662
Long-term Investments [Member] | U.S. Government And Agency Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Long-term		20,539
Gross Unrealized Losses, Long-term		(31)
Fair Value, Long-term		$ 20,508