CREDIT QUALITY ASSESSMENT - Information on the credit quality of loan portfolio under the new CECL (Detail) - Non-accrual status - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 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	421	85,286
Non-accrual balances transferred to OREO	0	(70)
Non-accrual balances charged-off	(699)	(1,394)
Net payments or draws	(16,028)	(21,201)
Non-accrual loans brought current	(55)	(1,976)
Balance at end of period	96,000	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	0	37,882
Non-accrual balances transferred to OREO	0	0
Non-accrual balances charged-off	0	(411)
Net payments or draws	(2,451)	(10,225)
Non-accrual loans brought current	0	0
Balance at end of period	42,776	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	0	8,572
Non-accrual balances transferred to OREO	0	0
Non-accrual balances charged-off	0	0
Net payments or draws	(3,245)	(1,059)
Non-accrual loans brought current	0	(100)
Balance at end of period	8,316	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	0	15,844
Non-accrual balances transferred to OREO	0	0
Non-accrual balances charged-off	0	0
Net payments or draws	(69)	(1,629)
Non-accrual loans brought current	0	0
Balance at end of period	14,975	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	84	17,442
Non-accrual balances transferred to OREO	0	0
Non-accrual balances charged-off	(650)	(446)
Net payments or draws	(9,220)	(4,169)
Non-accrual loans brought current	0	(883)
Balance at end of period	13,147	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	140	1,485
Non-accrual balances transferred to OREO	0	(70)
Non-accrual balances charged-off	0	(416)
Net payments or draws	(759)	(2,598)
Non-accrual loans brought current	0	(858)
Balance at end of period	9,593	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	0	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	0	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	197	4,061
Non-accrual balances transferred to OREO	0	0
Non-accrual balances charged-off	(49)	(121)
Net payments or draws	(284)	(1,521)
Non-accrual loans brought current	(55)	(135)
Balance at end of period	$ 7,193	$ 7,384