CREDIT QUALITY ASSESSMENT - Information about credit quality indicator by year of origination (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	$ 2,214,461	$ 3,305,720
Year two	1,799,826	1,774,275
Year three	1,436,996	1,179,845
Year four	948,283	1,016,641
Year five	787,183	866,898
Prior	1,544,326	1,242,626
Revolving Loans	990,273	1,014,504
Total	9,721,348	10,400,509
Commercial investor real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	779,888	922,059
Year two	787,845	767,459
Year three	622,526	466,934
Year four	418,191	470,150
Year five	381,383	470,019
Prior	731,639	504,568
Revolving Loans	22,226	33,531
Total	3,743,698	3,634,720
Commercial investor real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	764,573	910,426
Year two	782,273	763,214
Year three	613,930	448,406
Year four	408,936	448,698
Year five	370,635	469,077
Prior	723,877	498,384
Revolving Loans	22,226	33,531
Total	3,686,450	3,571,736
Commercial investor real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	2,283	11,044
Year two	4,980	0
Year three	4,276	4,879
Year four	602	833
Year five	684	269
Prior	6,924	27
Revolving Loans	0	0
Total	19,749	17,052
Commercial investor real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	13,032	589
Year two	592	4,245
Year three	4,320	13,649
Year four	8,653	20,619
Year five	10,064	673
Prior	838	6,157
Revolving Loans	0	0
Total	37,499	45,932
Commercial investor real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	0
Revolving Loans	0	0
Total	0	0
Commercial owner-occupied real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	268,856	289,210
Year two	262,413	389,393
Year three	334,578	239,670
Year four	204,447	197,841
Year five	179,248	205,278
Prior	406,795	319,160
Revolving Loans	4,755	1,664
Total	1,661,092	1,642,216
Commercial owner-occupied real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	267,459	285,310
Year two	258,309	385,058
Year three	326,143	234,578
Year four	199,446	192,634
Year five	174,397	204,925
Prior	394,812	306,840
Revolving Loans	4,755	1,664
Total	1,625,321	1,611,009
Commercial owner-occupied real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	160	2,290
Year two	1,519	0
Year three	4,301	3,027
Year four	2,721	4,742
Year five	4,492	134
Prior	9,210	4,079
Revolving Loans	0	0
Total	22,403	14,272
Commercial owner-occupied real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1,237	1,610
Year two	2,585	4,335
Year three	4,134	2,065
Year four	2,280	465
Year five	359	219
Prior	2,773	8,009
Revolving Loans	0	0
Total	13,368	16,703
Commercial owner-occupied real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	232
Revolving Loans	0	0
Total	0	232
Commercial AD&C
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	382,547	488,781
Year two	249,202	262,428
Year three	240,981	149,703
Year four	106,188	64,008
Year five	28,991	2,932
Prior	0	2,357
Revolving Loans	170,040	80,764
Total	1,177,949	1,050,973
Commercial AD&C | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	373,212	485,631
Year two	248,812	261,537
Year three	240,404	149,703
Year four	106,188	50,192
Year five	28,985	89
Prior	0	2,357
Revolving Loans	169,051	80,764
Total	1,166,652	1,030,273
Commercial AD&C | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	9,286	1,711
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	0
Revolving Loans	989	0
Total	10,275	1,711
Commercial AD&C | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	49	1,439
Year two	390	891
Year three	577	0
Year four	0	13,816
Year five	6	2,843
Prior	0	0
Revolving Loans	0	0
Total	1,022	18,989
Commercial AD&C | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	0
Revolving Loans	0	0
Total	0	0
Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	148,546	236,909
Year two	181,639	85,106
Year three	62,008	158,382
Year four	95,396	188,970
Year five	125,452	143,557
Prior	298,956	292,255
Revolving Loans	0	0
Total	911,997	1,105,179
Residential mortgage | 660-850
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	137,853	229,033
Year two	170,633	74,054
Year three	54,052	138,824
Year four	81,896	172,493
Year five	118,267	129,701
Prior	255,214	251,065
Revolving Loans	0	0
Total	817,915	995,170
Residential mortgage | 600-659
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	9,209	4,824
Year two	4,443	7,706
Year three	4,375	10,763
Year four	7,036	11,719
Year five	4,063	8,173
Prior	23,653	21,424
Revolving Loans	0	0
Total	52,779	64,609
Residential mortgage | 540-599
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	499	350
Year two	1,379	1,238
Year three	1,822	5,219
Year four	4,737	2,608
Year five	2,469	4,791
Prior	10,596	10,167
Revolving Loans	0	0
Total	21,502	24,373
Residential mortgage | less than 540
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	985	2,702
Year two	5,184	2,108
Year three	1,759	3,576
Year four	1,727	2,150
Year five	653	892
Prior	9,493	9,599
Revolving Loans	0	0
Total	19,801	21,027
Residential construction
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	96,440	115,201
Year two	65,743	47,836
Year three	10,202	14,543
Year four	6,130	2,805
Year five	1,248	2,062
Prior	1,556	0
Revolving Loans	0	172
Total	181,319	182,619
Residential construction | 660-850
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	95,213	112,604
Year two	65,743	44,647
Year three	9,013	14,543
Year four	6,130	2,805
Year five	1,248	1,693
Prior	1,160	0
Revolving Loans	0	172
Total	178,507	176,464
Residential construction | 600-659
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	195	1,743
Year two	0	3,189
Year three	1,189	0
Year four	0	0
Year five	0	0
Prior	396	0
Revolving Loans	0	0
Total	1,780	4,932
Residential construction | 540-599
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	369
Prior	0	0
Revolving Loans	0	0
Total	0	369
Residential construction | less than 540
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1,032	854
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	0
Revolving Loans	0	0
Total	1,032	854
Commercial Business
Financing Receivable, Credit Quality Indicator [Line Items]
Total	8,177,267	8,595,457
Commercial Business | Commercial business
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	534,428	1,249,771
Year two	251,276	215,623
Year three	161,996	144,348
Year four	113,049	89,205
Year five	68,581	38,836
Prior	66,116	87,689
Revolving Loans	399,082	442,076
Total	1,594,528	2,267,548
Commercial Business | Commercial business | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	532,473	1,244,822
Year two	245,034	208,682
Year three	151,622	138,861
Year four	110,341	86,830
Year five	66,806	34,498
Prior	61,688	81,760
Revolving Loans	389,218	433,016
Total	1,557,182	2,228,469
Commercial Business | Commercial business | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	109	1,929
Year two	2,247	1,382
Year three	7,634	1,119
Year four	1,711	708
Year five	673	309
Prior	554	621
Revolving Loans	8,094	4,319
Total	21,022	10,387
Commercial Business | Commercial business | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1,846	2,914
Year two	3,995	4,564
Year three	2,740	3,519
Year four	997	1,631
Year five	1,102	2,745
Prior	3,874	3,456
Revolving Loans	1,770	1,829
Total	16,324	20,658
Commercial Business | Commercial business | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	106
Year two	0	995
Year three	0	849
Year four	0	36
Year five	0	1,284
Prior	0	1,852
Revolving Loans	0	2,912
Total	0	8,034
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	3,756	3,789
Year two	1,708	6,430
Year three	4,705	6,265
Year four	4,882	3,662
Year five	2,280	4,214
Prior	39,264	36,597
Revolving Loans	394,170	456,297
Total	450,765	517,254
Consumer | 660-850
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	3,312	2,575
Year two	1,441	4,609
Year three	3,531	5,112
Year four	3,632	2,110
Year five	1,571	2,614
Prior	29,118	24,444
Revolving Loans	367,144	417,737
Total	409,749	459,201
Consumer | 600-659
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	220	374
Year two	196	445
Year three	329	334
Year four	591	428
Year five	481	467
Prior	5,278	5,401
Revolving Loans	14,135	21,052
Total	21,230	28,501
Consumer | 540-599
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	104	89
Year two	15	1,216
Year three	241	294
Year four	186	339
Year five	161	601
Prior	2,563	3,926
Revolving Loans	6,165	6,153
Total	9,435	12,618
Consumer | less than 540
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	120	751
Year two	56	160
Year three	604	525
Year four	473	785
Year five	67	532
Prior	2,305	2,826
Revolving Loans	6,726	11,355
Total	$ 10,351	$ 16,934