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	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 675,726	$ 2,129,465
2020	1,820,404	954,344
2019	918,378	804,015
2018	771,351	840,334
2017	782,919	666,584
Prior	2,475,232	1,975,259
Revolving loans amortized cost basis	774,746	924,822
Revolving loans converted to term loans	74,301	53,985
Total	8,293,057	8,348,808
Commercial real estate loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	293,370	988,831
2020	991,004	698,744
2019	690,560	639,959
2018	616,387	668,892
2017	628,881	570,031
Prior	2,144,913	1,710,506
Revolving loans amortized cost basis	185,651	198,663
Revolving loans converted to term loans	46,015	25,883
Total	5,596,781	5,501,509
Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	876	14,511
2020	19,034	9,350
2019	7,974	14,945
2018	14,153	2,258
2017	2,257	0
Prior	4	4
Revolving loans amortized cost basis	52,058	44,077
Revolving loans converted to term loans	0	0
Total	96,356	85,145
SBA [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	20,599	47,901
2020	44,593	12,821
2019	12,742	45,854
2018	44,039	69,788
2017	66,312	29,026
Prior	116,466	95,530
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	2,976	2,976
Total	307,727	303,896
SBA - Paycheck Protection Program (PPP) [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	314,940	882,986
2020	582,784	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	897,724	882,986
Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	34,603	110,819
2020	103,977	169,991
2019	150,461	68,341
2018	64,613	59,353
2017	53,230	32,529
Prior	102,945	80,995
Revolving loans amortized cost basis	235,939	281,322
Revolving loans converted to term loans	7,940	8,712
Total	753,708	812,062
Dairy And Livestock And Agribusiness [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	1,919
2020	2,216	1,765
2019	1,660	2,347
2018	1,708	6,373
2017	256	2,405
Prior	2,075	320
Revolving loans amortized cost basis	238,696	332,466
Revolving loans converted to term loans	14,477	13,551
Total	261,088	361,146
Municipal Lease Finance Receivables [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	8,478
2020	8,217	0
2019	0	2,556
2018	2,556	10,249
2017	10,248	3,586
Prior	21,328	20,678
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	42,349	45,547
SFR mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	7,745	65,463
2020	61,021	59,596
2019	53,148	29,142
2018	27,117	22,452
2017	20,857	27,421
Prior	85,084	66,002
Revolving loans amortized cost basis	2	3
Revolving loans converted to term loans	426	432
Total	255,400	270,511
Consumer Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	3,593	8,557
2020	7,558	2,077
2019	1,833	871
2018	778	969
2017	878	1,586
Prior	2,417	1,224
Revolving loans amortized cost basis	62,400	68,291
Revolving loans converted to term loans	2,467	2,431
Total	81,924	86,006
Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	661,202	2,112,914
2020	1,806,255	944,750
2019	903,769	763,869
2018	728,915	774,130
2017	709,596	640,874
Prior	2,371,362	1,893,124
Revolving loans amortized cost basis	741,275	880,898
Revolving loans converted to term loans	47,251	35,633
Total	7,969,625	8,046,192
Pass [Member] \| Commercial real estate loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	282,950	979,499
2020	981,750	691,091
2019	678,640	607,753
2018	588,405	617,640
2017	569,006	550,105
Prior	2,063,996	1,646,876
Revolving loans amortized cost basis	180,542	192,583
Revolving loans converted to term loans	35,794	24,548
Total	5,381,083	5,310,095
Pass [Member] \| Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	876	14,511
2020	19,034	9,350
2019	7,974	14,945
2018	6,380	2,258
2017	2,257	0
Prior	4	4
Revolving loans amortized cost basis	52,058	44,077
Revolving loans converted to term loans	0	0
Total	88,583	85,145
Pass [Member] \| SBA [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	20,599	47,901
2020	44,593	12,821
2019	12,742	44,950
2018	43,163	58,839
2017	55,759	26,136
Prior	104,385	86,085
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	2,976	2,976
Total	284,217	279,708
Pass [Member] \| SBA - Paycheck Protection Program (PPP) [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	314,940	882,986
2020	581,281	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	896,221	882,986
Pass [Member] \| Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	31,474	104,478
2020	100,585	168,050
2019	147,772	62,453
2018	59,414	56,043
2017	50,335	32,149
Prior	97,792	76,019
Revolving loans amortized cost basis	219,271	257,250
Revolving loans converted to term loans	6,303	6,058
Total	712,946	762,500
Pass [Member] \| Dairy And Livestock And Agribusiness [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	1,041
2020	2,216	1,765
2019	1,660	1,199
2018	1,102	5,680
2017	256	120
Prior	391	320
Revolving loans amortized cost basis	227,667	319,211
Revolving loans converted to term loans	387	363
Total	233,679	329,699
Pass [Member] \| Municipal Lease Finance Receivables [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	8,478
2020	8,217	0
2019	0	2,556
2018	2,556	10,249
2017	10,248	3,586
Prior	20,916	20,266
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	41,937	45,135
Pass [Member] \| SFR mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	7,745	65,463
2020	61,021	59,596
2019	53,148	29,142
2018	27,117	22,452
2017	20,857	27,192
Prior	81,721	62,593
Revolving loans amortized cost basis	2	3
Revolving loans converted to term loans	0	0
Total	251,611	266,441
Pass [Member] \| Consumer Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,618	8,557
2020	7,558	2,077
2019	1,833	871
2018	778	969
2017	878	1,586
Prior	2,157	961
Revolving loans amortized cost basis	61,735	67,774
Revolving loans converted to term loans	1,791	1,688
Total	79,348	84,483
Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	11,881	12,205
2020	11,035	8,243
2019	13,322	32,305
2018	35,678	50,344
2017	57,075	18,829
Prior	80,613	61,325
Revolving loans amortized cost basis	26,639	36,887
Revolving loans converted to term loans	17,479	3,659
Total	253,722	223,797
Special Mention [Member] \| Commercial real estate loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	10,420	9,332
2020	9,254	7,162
2019	11,441	30,049
2018	25,826	43,870
2017	50,811	17,398
Prior	66,570	49,840
Revolving loans amortized cost basis	4,609	5,720
Revolving loans converted to term loans	9,890	994
Total	188,821	164,365
Special Mention [Member] \| Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	7,773	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	7,773	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	5,408	1,336
Prior	6,864	5,648
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	12,272	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	486	1,995
2020	1,781	1,081
2019	1,881	1,892
2018	1,732	1,028
2017	856	95
Prior	4,798	4,882
Revolving loans amortized cost basis	10,485	17,395
Revolving loans converted to term loans	247	1,132
Total	22,266	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	347	0
2017	0	0
Prior	1,684	0
Revolving loans amortized cost basis	11,029	13,255
Revolving loans converted to term loans	7,342	1,511
Total	20,402	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	412	412
Total	412	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	195	452
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	195	452
Special Mention [Member] \| Consumer Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	975	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	90	91
Revolving loans amortized cost basis	516	517
Revolving loans converted to term loans	0	22
Total	1,581	630
Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,643	4,346
2020	3,114	1,351
2019	1,287	7,841
2018	6,758	15,860
2017	16,248	6,881
Prior	23,257	20,810
Revolving loans amortized cost basis	6,832	7,037
Revolving loans converted to term loans	9,571	14,693
Total	69,710	78,819
Substandard [Member] \| Commercial real estate loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	491
2019	479	2,157
2018	2,156	7,382
2017	9,064	2,528
Prior	14,347	13,790
Revolving loans amortized cost basis	500	360
Revolving loans converted to term loans	331	341
Total	26,877	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	876	5,503
2017	5,145	1,554
Prior	5,217	3,797
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	0	0
Total	11,238	11,758
Substandard [Member] \| SBA - Paycheck Protection Program (PPP) [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	1,503	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	1,503	0
Substandard [Member] \| Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,643	4,346
2020	1,611	860
2019	808	3,996
2018	3,467	2,282
2017	2,039	285
Prior	355	94
Revolving loans amortized cost basis	6,183	6,677
Revolving loans converted to term loans	1,390	1,522
Total	18,496	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	259	693
2017	0	2,285
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	6,748	11,677
Total	7,007	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	3,168	2,957
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans	426	432
Total	3,594	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	170	172
Revolving loans amortized cost basis	149	0
Revolving loans converted to term loans	676	721
Total	995	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
2017	0	0
Prior	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