CREDIT QUALITY ASSESSMENT - Allowance for Credit or Loan Losses by Respective Loan Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 109,145	$ 165,367	$ 165,367
Provision/ (credit) for credit losses	1,635	(34,708)	(45,556)
Charge-offs	(306)	(743)	(12,313)
Recoveries	114	445	1,647
Net recoveries (charge-offs)	(192)	(298)	(10,666)
Balance at period end	110,588	130,361	109,145
Total loans	$ 10,144,328		$ 9,967,091
Allowance for credit losses to total loans ratio	1.09%		1.10%
Average loans	$ 9,965,499		$ 10,034,866
Annualized net charge-offs/ (recoveries) to average loans	0.01%		0.11%
Balance of loans individually evaluated for credit loss	$ 31,773		$ 33,534
Allowance related to loans evaluated individually	$ 6,654		$ 6,593
Individual allowance to loans evaluated individually ratio	20.94%		19.66%
Balance of loans collectively evaluated for credit loss	$ 10,112,555		$ 9,933,557
Allowance related to loans evaluated collectively	$ 103,934		$ 102,552
Collective allowance to loans evaluated collectively ratio	1.03%		1.03%
Commercial investor real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs	$ 0		$ (5,802)
Total loans	4,388,275		4,141,346
Commercial owner-occupied real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs	0		(136)
Total loans	1,692,253		1,690,881
Commercial AD&C
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs	0		(2,007)
Total loans	1,089,331		1,088,094
Residential mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs	(132)		0
Total loans	1,000,697		937,570
Residential construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs	0		0
Total loans	204,259		197,652
Commercial real estate: | Commercial investor real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	45,289	57,404	57,404
Provision/ (credit) for credit losses	5,505		(6,598)
Charge-offs	0		(5,802)
Recoveries	19		285
Net recoveries (charge-offs)	19		(5,517)
Balance at period end	50,813		45,289
Total loans	$ 4,388,275		$ 4,141,346
Allowance for credit losses to total loans ratio	1.16%		1.09%
Average loans	$ 4,220,246		$ 3,689,769
Annualized net charge-offs/ (recoveries) to average loans	0.00%		0.15%
Balance of loans individually evaluated for credit loss	$ 11,743		$ 12,489
Allowance related to loans evaluated individually	$ 181		$ 213
Individual allowance to loans evaluated individually ratio	1.54%		1.71%
Balance of loans collectively evaluated for credit loss	$ 4,376,532		$ 4,128,857
Allowance related to loans evaluated collectively	$ 50,632		$ 45,076
Collective allowance to loans evaluated collectively ratio	1.16%		1.09%
Commercial real estate: | Commercial owner-occupied real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 11,687	20,061	$ 20,061
Provision/ (credit) for credit losses	(827)		(8,238)
Charge-offs	0		(136)
Recoveries	0		0
Net recoveries (charge-offs)	0		(136)
Balance at period end	10,860		11,687
Total loans	$ 1,692,253		$ 1,690,881
Allowance for credit losses to total loans ratio	0.64%		0.69%
Average loans	$ 1,683,557		$ 1,661,015
Annualized net charge-offs/ (recoveries) to average loans	0.00%		0.01%
Balance of loans individually evaluated for credit loss	$ 8,083		$ 9,306
Allowance related to loans evaluated individually	$ 94		$ 79
Individual allowance to loans evaluated individually ratio	1.16%		0.85%
Balance of loans collectively evaluated for credit loss	$ 1,684,170		$ 1,681,575
Allowance related to loans evaluated collectively	$ 10,766		$ 11,608
Collective allowance to loans evaluated collectively ratio	0.64%		0.69%
Commercial real estate: | Commercial AD&C
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 20,322	22,157	$ 22,157
Provision/ (credit) for credit losses	(1,863)		172
Charge-offs	0		(2,007)
Recoveries	0		0
Net recoveries (charge-offs)	0		(2,007)
Balance at period end	18,459		20,322
Total loans	$ 1,089,331		$ 1,088,094
Allowance for credit losses to total loans ratio	1.69%		1.87%
Average loans	$ 1,102,660		$ 1,110,420
Annualized net charge-offs/ (recoveries) to average loans	0.00%		0.18%
Balance of loans individually evaluated for credit loss	$ 1,081		$ 650
Allowance related to loans evaluated individually	$ 504		$ 504
Individual allowance to loans evaluated individually ratio	46.62%		77.54%
Balance of loans collectively evaluated for credit loss	$ 1,088,250		$ 1,087,444
Allowance related to loans evaluated collectively	$ 17,955		$ 19,818
Collective allowance to loans evaluated collectively ratio	1.65%		1.82%
Commercial Business
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Total loans	$ 8,519,461		$ 8,402,155
Balance of loans individually evaluated for credit loss	8,982		9,033
Allowance related to loans evaluated individually	5,875		5,797
Commercial Business | Commercial business
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	23,170	46,806	46,806
Provision/ (credit) for credit losses	(1,288)		(20,132)
Charge-offs	(118)		(4,069)
Recoveries	7		565
Net recoveries (charge-offs)	(111)		(3,504)
Balance at period end	21,771		23,170
Total loans	$ 1,349,602		$ 1,481,834
Allowance for credit losses to total loans ratio	1.61%		1.56%
Average loans	$ 1,372,755		$ 1,952,537
Annualized net charge-offs/ (recoveries) to average loans	0.03%		0.18%
Balance of loans individually evaluated for credit loss	$ 8,982		$ 9,033
Allowance related to loans evaluated individually	$ 5,875		$ 5,797
Individual allowance to loans evaluated individually ratio	65.41%		64.18%
Balance of loans collectively evaluated for credit loss	$ 1,340,620		$ 1,472,801
Allowance related to loans evaluated collectively	$ 15,896		$ 17,373
Collective allowance to loans evaluated collectively ratio	1.19%		1.18%
Residential real estate: | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 5,384	11,295	$ 11,295
Provision/ (credit) for credit losses	458		(6,321)
Charge-offs	(132)		0
Recoveries	12		410
Net recoveries (charge-offs)	(120)		410
Balance at period end	5,722		5,384
Total loans	$ 1,000,697		$ 937,570
Allowance for credit losses to total loans ratio	0.57%		0.57%
Average loans	$ 964,056		$ 979,754
Annualized net charge-offs/ (recoveries) to average loans	0.05%		(0.04%)
Balance of loans individually evaluated for credit loss	$ 1,536		$ 1,704
Allowance related to loans evaluated individually	$ 0		$ 0
Individual allowance to loans evaluated individually ratio	0.00%		0.00%
Balance of loans collectively evaluated for credit loss	$ 999,161		$ 935,866
Allowance related to loans evaluated collectively	$ 5,722		$ 5,384
Collective allowance to loans evaluated collectively ratio	0.57%		0.58%
Residential real estate: | Residential construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 1,048	1,502	$ 1,502
Provision/ (credit) for credit losses	(159)		(459)
Charge-offs	0		0
Recoveries	0		5
Net recoveries (charge-offs)	0		5
Balance at period end	889		1,048
Total loans	$ 204,259		$ 197,652
Allowance for credit losses to total loans ratio	0.44%		0.53%
Average loans	$ 197,366		$ 178,171
Annualized net charge-offs/ (recoveries) to average loans	0.00%		0.00%
Balance of loans individually evaluated for credit loss	$ 0		$ 0
Allowance related to loans evaluated individually	$ 0		$ 0
Individual allowance to loans evaluated individually ratio	0.00%		0.00%
Balance of loans collectively evaluated for credit loss	$ 204,259		$ 197,652
Allowance related to loans evaluated collectively	$ 889		$ 1,048
Collective allowance to loans evaluated collectively ratio	0.44%		0.53%
Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 2,245	$ 6,142	$ 6,142
Provision/ (credit) for credit losses	(191)		(3,980)
Charge-offs	(56)		(299)
Recoveries	76		382
Net recoveries (charge-offs)	20		83
Balance at period end	2,074		2,245
Total loans	$ 419,911		$ 429,714
Allowance for credit losses to total loans ratio	0.49%		0.52%
Average loans	$ 424,859		$ 463,200
Annualized net charge-offs/ (recoveries) to average loans	(0.02%)		(0.02%)
Balance of loans individually evaluated for credit loss	$ 348		$ 352
Allowance related to loans evaluated individually	$ 0		$ 0
Individual allowance to loans evaluated individually ratio	0.00%		0.00%
Balance of loans collectively evaluated for credit loss	$ 419,563		$ 429,362
Allowance related to loans evaluated collectively	$ 2,074		$ 2,245
Collective allowance to loans evaluated collectively ratio	0.49%		0.52%