Loans and Lease Finance Receivables and Allowance for Credit Losses - Summary of loans by type and origination year, according to our internal risk ratings (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 1,389,874	$ 2,129,465
2020	1,256,695	954,344
2019	833,328	804,015
2018	698,128	840,334
2017	681,030	666,584
Prior	2,138,706	1,975,259
Revolving loans amortized cost basis	776,209	924,822
Revolving loans converted to term loans	75,550	53,985
Total	7,849,520	8,348,808
Commercial real estate loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	893,291	988,831
2020	985,227	698,744
2019	632,215	639,959
2018	569,838	668,892
2017	560,293	570,031
Prior	1,867,451	1,710,506
Revolving loans amortized cost basis	175,776	198,663
Revolving loans converted to term loans	50,608	25,883
Total	5,734,699	5,501,509
Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	7,465	14,511
2020	22,258	9,350
2019	7,148	14,945
2018	3,142	2,258
2017	0	0
Prior	0	4
Revolving loans amortized cost basis	37,385	44,077
Revolving loans converted to term loans	0	0
Total	77,398	85,145
SBA [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	63,286	47,901
2020	42,468	12,821
2019	11,233	45,854
2018	39,758	69,788
2017	53,483	29,026
Prior	97,305	95,530
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	2,976
Total	307,533	303,896
SBA - Paycheck Protection Program (PPP) [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	278,560	882,986
2020	52,400	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	330,960	882,986
Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	104,241	110,819
2020	89,883	169,991
2019	135,326	68,341
2018	63,210	59,353
2017	39,778	32,529
Prior	82,751	80,995
Revolving loans amortized cost basis	245,224	281,322
Revolving loans converted to term loans	9,564	8,712
Total	769,977	812,062
Dairy And Livestock And Agribusiness [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	13	1,919
2020	988	1,765
2019	1,420	2,347
2018	1,271	6,373
2017	126	2,405
Prior	322	320
Revolving loans amortized cost basis	263,526	332,466
Revolving loans converted to term loans	11,918	13,551
Total	279,584	361,146
Municipal Lease Finance Receivables [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	9,557	8,478
2020	7,875	0
2019	0	2,556
2018	279	10,249
2017	9,720	3,586
Prior	19,874	20,678
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	47,305	45,547
SFR mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	27,356	65,463
2020	52,771	59,596
2019	44,447	29,142
2018	20,072	22,452
2017	17,176	27,421
Prior	68,935	66,002
Revolving loans amortized cost basis	152	3
Revolving loans converted to term loans	414	432
Total	231,323	270,511
Consumer Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	6,105	8,557
2020	2,825	2,077
2019	1,539	871
2018	558	969
2017	454	1,586
Prior	2,068	1,224
Revolving loans amortized cost basis	54,146	68,291
Revolving loans converted to term loans	3,046	2,431
Total	70,741	86,006
Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	1,370,969	2,112,914
2020	1,247,237	944,750
2019	822,680	763,869
2018	671,770	774,130
2017	621,292	640,874
Prior	2,071,359	1,893,124
Revolving loans amortized cost basis	756,161	880,898
Revolving loans converted to term loans	53,792	35,633
Total	7,615,260	8,046,192
Pass [Member] \| Commercial real estate loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	878,859	979,499
2020	979,652	691,091
2019	622,674	607,753
2018	547,936	617,640
2017	511,804	550,105
Prior	1,812,200	1,646,876
Revolving loans amortized cost basis	169,358	192,583
Revolving loans converted to term loans	44,792	24,548
Total	5,567,275	5,310,095
Pass [Member] \| Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	7,465	14,511
2020	22,258	9,350
2019	7,148	14,945
2018	3,142	2,258
2017	0	0
Prior	0	4
Revolving loans amortized cost basis	37,385	44,077
Revolving loans converted to term loans	0	0
Total	77,398	85,145
Pass [Member] \| SBA [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	63,286	47,901
2020	42,468	12,821
2019	11,233	44,950
2018	38,918	58,839
2017	43,891	26,136
Prior	88,592	86,085
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	2,976
Total	288,388	279,708
Pass [Member] \| SBA - Paycheck Protection Program (PPP) [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	278,560	882,986
2020	50,877	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	329,437	882,986
Pass [Member] \| Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	100,677	104,478
2020	87,523	168,050
2019	134,219	62,453
2018	59,713	56,043
2017	38,121	32,149
Prior	81,999	76,019
Revolving loans amortized cost basis	237,284	257,250
Revolving loans converted to term loans	5,919	6,058
Total	745,455	762,500
Pass [Member] \| Dairy And Livestock And Agribusiness [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	13	1,041
2020	988	1,765
2019	1,420	1,199
2018	1,152	5,680
2017	126	120
Prior	322	320
Revolving loans amortized cost basis	258,432	319,211
Revolving loans converted to term loans	886	363
Total	263,339	329,699
Pass [Member] \| Municipal Lease Finance Receivables [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	9,557	8,478
2020	7,875	0
2019	0	2,556
2018	279	10,249
2017	9,720	3,586
Prior	19,498	20,266
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	46,929	45,135
Pass [Member] \| SFR mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	27,356	65,463
2020	52,771	59,596
2019	44,447	29,142
2018	20,072	22,452
2017	17,176	27,192
Prior	66,847	62,593
Revolving loans amortized cost basis	152	3
Revolving loans converted to term loans	0	0
Total	228,821	266,441
Pass [Member] \| Consumer Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	5,196	8,557
2020	2,825	2,077
2019	1,539	871
2018	558	969
2017	454	1,586
Prior	1,901	961
Revolving loans amortized cost basis	53,550	67,774
Revolving loans converted to term loans	2,195	1,688
Total	68,218	84,483
Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	13,816	12,205
2020	7,928	8,243
2019	10,079	32,305
2018	23,383	50,344
2017	48,248	18,829
Prior	52,950	61,325
Revolving loans amortized cost basis	19,700	36,887
Revolving loans converted to term loans	8,401	3,659
Total	184,505	223,797
Special Mention [Member] \| Commercial real estate loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	11,986	9,332
2020	5,575	7,162
2019	9,078	30,049
2018	21,902	43,870
2017	43,612	17,398
Prior	46,359	49,840
Revolving loans amortized cost basis	6,418	5,720
Revolving loans converted to term loans	5,500	994
Total	150,430	164,365
Special Mention [Member] \| Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	0	0
Special Mention [Member] \| SBA [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	5,446
2017	4,121	1,336
Prior	6,075	5,648
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	10,196	12,430
Special Mention [Member] \| SBA - Paycheck Protection Program (PPP) [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	0	0
Special Mention [Member] \| Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	921	1,995
2020	2,353	1,081
2019	1,001	1,892
2018	1,481	1,028
2017	515	95
Prior	140	4,882
Revolving loans amortized cost basis	7,597	17,395
Revolving loans converted to term loans	198	1,132
Total	14,206	29,500
Special Mention [Member] \| Dairy And Livestock And Agribusiness [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	878
2020	0	0
2019	0	364
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	5,094	13,255
Revolving loans converted to term loans	2,300	1,511
Total	7,394	16,008
Special Mention [Member] \| Municipal Lease Finance Receivables [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	376	412
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	376	412
Special Mention [Member] \| SFR mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	452
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	0	452
Special Mention [Member] \| Consumer Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	909	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	91
Revolving loans amortized cost basis	591	517
Revolving loans converted to term loans	403	22
Total	1,903	630
Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	5,089	4,346
2020	1,530	1,351
2019	569	7,841
2018	2,975	15,860
2017	11,490	6,881
Prior	14,397	20,810
Revolving loans amortized cost basis	348	7,037
Revolving loans converted to term loans	13,357	14,693
Total	49,755	78,819
Substandard [Member] \| Commercial real estate loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,446	0
2020	0	491
2019	463	2,157
2018	0	7,382
2017	4,877	2,528
Prior	8,892	13,790
Revolving loans amortized cost basis	0	360
Revolving loans converted to term loans	316	341
Total	16,994	27,049
Substandard [Member] \| Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	0	0
Substandard [Member] \| SBA [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	904
2018	840	5,503
2017	5,471	1,554
Prior	2,638	3,797
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	8,949	11,758
Substandard [Member] \| SBA - Paycheck Protection Program (PPP) [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	1,523	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	1,523	0
Substandard [Member] \| Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,643	4,346
2020	7	860
2019	106	3,996
2018	2,016	2,282
2017	1,142	285
Prior	612	94
Revolving loans amortized cost basis	343	6,677
Revolving loans converted to term loans	3,447	1,522
Total	10,316	20,062
Substandard [Member] \| Dairy And Livestock And Agribusiness [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	784
2018	119	693
2017	0	2,285
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	8,732	11,677
Total	8,851	15,439
Substandard [Member] \| Municipal Lease Finance Receivables [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	0	0
Substandard [Member] \| SFR mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	229
Prior	2,088	2,957
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	414	432
Total	2,502	3,618
Substandard [Member] \| Consumer Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	167	172
Revolving loans amortized cost basis	5	0
Revolving loans converted to term loans	448	721
Total	620	893
Doubtful [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	0	0
Doubtful [Member] \| Commercial real estate loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	0	0
Doubtful [Member] \| Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	0	0
Doubtful [Member] \| SBA [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	0	0
Doubtful [Member] \| SBA - Paycheck Protection Program (PPP) [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	0	0
Doubtful [Member] \| Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0

Loans and Lease Finance Receivables and Allowance for Credit Losses - Summary of loans by type and origination year, according to our internal risk ratings (Detail) - USD ($)
$ in Thousands