ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Reclassified Out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Amounts reclassified out of each component of accumulated other comprehensive income
Net gains (losses) on sales of investment securities									$ 150	$ (201)	$ 36
Income tax benefit (expense)	$ (7,605)	$ (6,814)	$ (5,887)	$ (5,452)	$ (3,772)	$ (2,200)	$ (2,967)	$ (2,821)	(25,758)	(11,760)	(19,605)
Net of tax									(41,387)	16,140	37,660
Total reclassifications, net of tax	$ 22,327	$ 20,815	$ 18,714	$ 18,038	$ 12,171	$ 6,859	$ 9,917	$ 8,326	79,894	37,273	58,322
Amount Reclassified from AOCI
Amounts reclassified out of each component of accumulated other comprehensive income
Total reclassifications, net of tax									(649)	(1,020)	(818)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Amounts reclassified out of each component of accumulated other comprehensive income
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax									(1,036)	(1,160)	(1,117)
Reclassification from AOCI, Current Period, Tax									(291)	(310)	(299)
Net of tax									(745)	(850)	(818)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member] | Amount Reclassified from AOCI
Amounts reclassified out of each component of accumulated other comprehensive income
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax									(1,036)	(1,160)	(1,117)
Accumulated Defined Benefit Plans Adjustment, Net Transition Attributable to Parent [Member]
Amounts reclassified out of each component of accumulated other comprehensive income
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax									(18)	(18)	(18)
Reclassification from AOCI, Current Period, Tax									(4)	(5)	(5)
Net of tax									(14)	(13)	(13)
Accumulated Defined Benefit Plans Adjustment, Net Transition Attributable to Parent [Member] | Amount Reclassified from AOCI
Amounts reclassified out of each component of accumulated other comprehensive income
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax									(18)	(18)	(18)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Amounts reclassified out of each component of accumulated other comprehensive income
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax									0	(14)	(18)
Reclassification from AOCI, Current Period, Tax									0	(4)	(5)
Net of tax									0	(10)	(13)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member] | Amount Reclassified from AOCI
Amounts reclassified out of each component of accumulated other comprehensive income
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax									0	(14)	(18)
Investment Securities
Amounts reclassified out of each component of accumulated other comprehensive income
Net of tax									110	(147)	26
Investment Securities | Amount Reclassified from AOCI
Amounts reclassified out of each component of accumulated other comprehensive income
Net gains (losses) on sales of investment securities									150	(201)	36
Income tax benefit (expense)									(40)	54	(10)
Net of tax									110	(147)	26
Defined Benefit Plans
Amounts reclassified out of each component of accumulated other comprehensive income
Net of tax									(759)	(873)	(844)
Defined Benefit Plans | Amount Reclassified from AOCI
Amounts reclassified out of each component of accumulated other comprehensive income
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax									(1,054)	(1,192)	(1,153)
Reclassification from AOCI, Current Period, Tax									(295)	(319)	(309)
Net of tax									$ (759)	$ (873)	$ (844)