ACCUMULATED OTHER COMPREHENSIVE INCOME/ (LOSS) - Net Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Mar. 31, 2022
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
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	$ 1,519,679	$ 1,469,955	$ 1,132,974
Period change, net of tax	(123,412)	(27,244)	23,037
Balance at end of period	1,483,768	1,519,679	1,469,955
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(8,539)	18,705	(4,332)
Period change, net of tax	(123,412)	(27,244)	23,037
Balance at end of period	(131,951)	(8,539)	18,705
Unrealized Gains/ (Losses) on Investments Available-for-Sale
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(336)	28,175	4,000
Period change, net of tax	(113,177)	(28,511)	24,175
Balance at end of period	(113,513)	(336)	28,175
Defined Benefit Pension Plan
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(8,203)	(9,470)	(8,332)
Period change, net of tax	201	1,267	(1,138)
Balance at end of period	(8,002)	(8,203)	(9,470)
Unrealized Losses on Debt Securities Transferred from Available-for-Sale to Held-to-Maturity
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	0	0	0
Period change, net of tax	(10,436)	0	0
Balance at end of period	$ (10,436)	$ 0	$ 0