ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Net Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortized cost of debt securities transferred to held-to-maturity	$ 305,600
After tax unrealized loss of debt securities transferred to held-to-maturity	12,100
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(8,539)
Other comprehensive loss before reclassification from accumulated other comprehensive income, net of tax	(61,109)
Reclassifications from accumulated other comprehensive income to earnings, net of tax	377
Total other comprehensive loss	(60,732)	$ (21,357)
Ending Balance	(69,271)
Unrealized Gains/(Losses) on Debt Securities Available-for-Sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(336)	28,175
Other comprehensive loss before reclassification from accumulated other comprehensive income, net of tax	(49,026)	(21,478)
Reclassifications from accumulated other comprehensive income to earnings, net of tax	(6)	(43)
Total other comprehensive loss	(49,032)	(21,521)
Ending Balance	(49,368)	6,654
Defined Benefit Pension Plan
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(8,203)	(9,470)
Other comprehensive loss before reclassification from accumulated other comprehensive income, net of tax	0	0
Reclassifications from accumulated other comprehensive income to earnings, net of tax	146	164
Total other comprehensive loss	146	164
Ending Balance	(8,057)	(9,306)
Unrealized Losses on Debt Securities Transferred from Available-for-Sale to Held-to-Maturity
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	0
Other comprehensive loss before reclassification from accumulated other comprehensive income, net of tax	(12,083)
Reclassifications from accumulated other comprehensive income to earnings, net of tax	237
Total other comprehensive loss	(11,846)
Ending Balance	(11,846)
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(8,539)	18,705
Other comprehensive loss before reclassification from accumulated other comprehensive income, net of tax		(21,478)
Reclassifications from accumulated other comprehensive income to earnings, net of tax		121
Total other comprehensive loss	(60,732)	(21,357)
Ending Balance	$ (69,271)	$ (2,652)