ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Net Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 18,705
Total other comprehensive income/ (loss)	(21,357)	$ 10,676
Ending Balance	(2,652)
Unrealized Gains on Investments Available-for-Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	28,175	4,000
Other comprehensive loss before reclassification, net of tax	(21,478)	10,639
Reclassifications from accumulated other comprehensive income, net of tax	(43)	(127)
Total other comprehensive income/ (loss)	(21,521)	10,512
Ending Balance	6,654	14,512
Defined Benefit Pension Plan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(9,470)	(8,332)
Other comprehensive loss before reclassification, net of tax	0	0
Reclassifications from accumulated other comprehensive income, net of tax	164	164
Total other comprehensive income/ (loss)	164	164
Ending Balance	(9,306)	(8,168)
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	18,705	(4,332)
Other comprehensive loss before reclassification, net of tax	(21,478)	10,639
Reclassifications from accumulated other comprehensive income, net of tax	121	37
Total other comprehensive income/ (loss)	(21,357)	10,676
Ending Balance	$ (2,652)	$ 6,344