Loans and Lease Finance Receivables and Allowance for Credit Losses - Schedule of Balance and Activity Related to Allowance for Loan Losses for Held-for-Investment Loans by Type (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	$ 76,119	$ 71,805	$ 65,019	$ 93,692
Charge-offs	8	510	24	2,985
Initial ACL for PCD Loans at Acquisition			8,605
Provision Recorded at Acquisition			4,932
Recoveries	511	47	522	135
Provision for (Recapture of) Credit Losses	3,600	(2,000)	1,168	(21,500)
Ending Balance	80,222	69,342	80,222	69,342
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	57,835	56,572	50,950	75,439
Charge-offs	0
Initial ACL for PCD Loans at Acquisition			5,086
Provision Recorded at Acquisition			4,127
Recoveries
Provision for (Recapture of) Credit Losses	3,678	1,372	1,350	(20,239)
Ending Balance	61,513	55,200	61,513	55,200
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	988	1,878	765	1,934
Charge-offs	0	0
Initial ACL for PCD Loans at Acquisition			122
Provision Recorded at Acquisition			58
Recoveries	3	41	6	44
Provision for (Recapture of) Credit Losses	71	(94)	111	(153)
Ending Balance	1,062	1,825	1,062	1,825
Small Business Administration [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	2,824	2,512	2,668	2,992
Charge-offs	0	0
Initial ACL for PCD Loans at Acquisition			62
Provision Recorded at Acquisition			64
Recoveries	53	4	58	8
Provision for (Recapture of) Credit Losses	(264)	30	(239)	(454)
Ending Balance	2,613	2,546	2,613	2,546
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	6,831	6,439	6,669	7,142
Charge-offs	6	500	21	2,975
Initial ACL for PCD Loans at Acquisition			500
Provision Recorded at Acquisition			508
Recoveries	453	2	456	4
Provision for (Recapture of) Credit Losses	(84)	(274)	(918)	1,496
Ending Balance	7,194	5,667	7,194	5,667
Dairy & Livestock and Agribusiness [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	6,703	2,722	3,066	3,949
Charge-offs	0	0
Initial ACL for PCD Loans at Acquisition			2,832
Provision Recorded at Acquisition			149
Recoveries	2	0	2
Provision for (Recapture of) Credit Losses	127	53	783	(1,174)
Ending Balance	6,832	2,775	6,832	2,775
Municipal Lease Finance Receivables [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	152	35	100	74
Charge-offs	0	0
Initial ACL for PCD Loans at Acquisition			3
Provision Recorded at Acquisition			26
Recoveries		0
Provision for (Recapture of) Credit Losses	31	32	54	(7)
Ending Balance	183	67	183	67
SFR Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	227	298	188	367
Charge-offs	0	0
Initial ACL for PCD Loans at Acquisition
Provision Recorded at Acquisition
Recoveries		0		79
Provision for (Recapture of) Credit Losses	27	(14)	66	(162)
Ending Balance	254	284	254	284
Consumer and Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	559	1,349	613	1,795
Charge-offs	2	10	3	10
Initial ACL for PCD Loans at Acquisition
Provision Recorded at Acquisition
Recoveries		0
Provision for (Recapture of) Credit Losses	14	(361)	(39)	(807)
Ending Balance	$ 571	$ 978	$ 571	$ 978