CREDIT QUALITY ASSESSMENT - Information on the credit quality of loan portfolio under the new CECL (Detail) - Non-accrual status - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 112,361	$ 38,632
PCD loans designed as non-accrual		13,084
Loans placed on non-accrual	7,635	85,286
Non-accrual balances transferred to OREO	(257)	(70)
Non-accrual balances charged-off	(10,839)	(1,394)
Net payments or draws	(55,444)	(21,201)
Non-accrual loans brought current	(341)	(1,976)
Balance at end of period	53,115	112,361
Commercial real estate: | Commercial investor real estate
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	45,227	8,437
PCD loans designed as non-accrual		9,544
Loans placed on non-accrual	699	37,882
Non-accrual balances transferred to OREO	0	0
Non-accrual balances charged-off	(5,803)	(411)
Net payments or draws	(24,737)	(10,225)
Non-accrual loans brought current	0	0
Balance at end of period	15,386	45,227
Commercial real estate: | Commercial owner-occupied real estate
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	11,561	4,148
PCD loans designed as non-accrual		0
Loans placed on non-accrual	3,676	8,572
Non-accrual balances transferred to OREO	(257)	0
Non-accrual balances charged-off	(136)	0
Net payments or draws	(4,990)	(1,059)
Non-accrual loans brought current	0	(100)
Balance at end of period	9,854	11,561
Commercial real estate: | Commercial AD&C
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	15,044	829
PCD loans designed as non-accrual		0
Loans placed on non-accrual	49	15,844
Non-accrual balances transferred to OREO	0	0
Non-accrual balances charged-off	(2,007)	0
Net payments or draws	(12,064)	(1,629)
Non-accrual loans brought current	0	0
Balance at end of period	1,022	15,044
Commercial Business
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	22,933	8,450
PCD loans designed as non-accrual		2,539
Loans placed on non-accrual	963	17,442
Non-accrual balances transferred to OREO	0	0
Non-accrual balances charged-off	(2,793)	(446)
Net payments or draws	(11,649)	(4,169)
Non-accrual loans brought current	0	(883)
Balance at end of period	9,454	22,933
Residential real estate: | Residential mortgage
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	10,212	12,661
PCD loans designed as non-accrual		8
Loans placed on non-accrual	687	1,485
Non-accrual balances transferred to OREO	0	(70)
Non-accrual balances charged-off	0	(416)
Net payments or draws	(1,328)	(2,598)
Non-accrual loans brought current	(60)	(858)
Balance at end of period	9,511	10,212
Residential real estate: | Residential construction
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	0	0
PCD loans designed as non-accrual		0
Loans placed on non-accrual	62	0
Non-accrual balances transferred to OREO	0	0
Non-accrual balances charged-off	0	0
Net payments or draws	0	0
Non-accrual loans brought current	0	0
Balance at end of period	62	0
Consumer
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	7,384	4,107
PCD loans designed as non-accrual		993
Loans placed on non-accrual	1,499	4,061
Non-accrual balances transferred to OREO	0	0
Non-accrual balances charged-off	(100)	(121)
Net payments or draws	(676)	(1,521)
Non-accrual loans brought current	(281)	(135)
Balance at end of period	$ 7,826	$ 7,384