ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Net Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 18,705
Other comprehensive loss before reclassification, net of tax			(20,218)
Reclassifications from accumulated other comprehensive income, net of tax			387
Total other comprehensive income/ (loss)	$ (5,960)	$ 2,669	(19,831)	$ 21,825
Ending Balance	(1,126)		(1,126)
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			(20,218)	21,650
Reclassifications from accumulated other comprehensive income, net of tax			(133)	(322)
Total other comprehensive income/ (loss)			(20,351)	21,328
Ending Balance	7,824	25,328	7,824	25,328
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			520	497
Total other comprehensive income/ (loss)			520	497
Ending Balance	(8,950)	(7,835)	(8,950)	(7,835)
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			18,705	(4,332)
Other comprehensive loss before reclassification, net of tax				21,650
Reclassifications from accumulated other comprehensive income, net of tax				175
Total other comprehensive income/ (loss)	(5,960)	2,669	(19,831)	21,825
Ending Balance	$ (1,126)	$ 17,493	$ (1,126)	$ 17,493