Loans Held for Investment - Delinquencies (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	$ 14,976,935
Loans held for investment	14,908,811	$ 14,295,897
Fair value hedging relationships	(68,124)	(5,298)
Current
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	14,935,678
Loans held for investment		14,276,402
30-59
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	1,484
Loans held for investment		1,395
60-89
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	6,535
Loans held for investment		0
90+
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	33,238
Loans held for investment		18,100
Investor loans secured by real estate
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	9,387,045
Loans held for investment	9,387,045	8,987,628
Investor loans secured by real estate | CRE non-owner-occupied
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,771,272
Loans held for investment	2,771,272	2,771,137
Investor loans secured by real estate | Multifamily
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	6,199,581
Loans held for investment	6,199,581	5,891,934
Investor loans secured by real estate | Construction and land
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	373,194
Loans held for investment	373,194	277,640
Investor loans secured by real estate | SBA secured by real estate
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	42,998
Loans held for investment	42,998	46,917
Investor loans secured by real estate | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	9,364,102
Loans held for investment		8,975,806
Investor loans secured by real estate | Current | CRE non-owner-occupied
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,754,403
Loans held for investment		2,760,882
Investor loans secured by real estate | Current | Multifamily
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	6,193,507
Loans held for investment		5,890,704
Investor loans secured by real estate | Current | Construction and land
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	373,194
Loans held for investment		277,640
Investor loans secured by real estate | Current | SBA secured by real estate
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	42,998
Loans held for investment		46,580
Investor loans secured by real estate | 30-59
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		1,230
Investor loans secured by real estate | 30-59 | CRE non-owner-occupied
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Investor loans secured by real estate | 30-59 | Multifamily
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		1,230
Investor loans secured by real estate | 30-59 | Construction and land
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Investor loans secured by real estate | 30-59 | SBA secured by real estate
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Investor loans secured by real estate | 60-89
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Investor loans secured by real estate | 60-89 | CRE non-owner-occupied
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Investor loans secured by real estate | 60-89 | Multifamily
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Investor loans secured by real estate | 60-89 | Construction and land
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Investor loans secured by real estate | 60-89 | SBA secured by real estate
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Investor loans secured by real estate | 90+
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	22,943
Loans held for investment		10,592
Investor loans secured by real estate | 90+ | CRE non-owner-occupied
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	16,869
Loans held for investment		10,255
Investor loans secured by real estate | 90+ | Multifamily
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	6,074
Loans held for investment		0
Investor loans secured by real estate | 90+ | Construction and land
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Investor loans secured by real estate | 90+ | SBA secured by real estate
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		337
Business loans secured by real estate
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,925,000
Loans held for investment	2,925,000	2,700,579
Business loans secured by real estate | SBA secured by real estate
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	64,002
Loans held for investment	64,002	69,184
Business loans secured by real estate | CRE owner-occupied
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,477,530
Loans held for investment	2,477,530	2,251,014
Business loans secured by real estate | Franchise real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	383,468
Loans held for investment	383,468	380,381
Business loans secured by real estate | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,912,424
Loans held for investment		2,695,186
Business loans secured by real estate | Current | SBA secured by real estate
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	62,675
Loans held for investment		68,743
Business loans secured by real estate | Current | CRE owner-occupied
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,466,281
Loans held for investment		2,246,062
Business loans secured by real estate | Current | Franchise real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	383,468
Loans held for investment		380,381
Business loans secured by real estate | 30-59
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	1,244
Loans held for investment		0
Business loans secured by real estate | 30-59 | SBA secured by real estate
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	1,244
Loans held for investment		0
Business loans secured by real estate | 30-59 | CRE owner-occupied
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Business loans secured by real estate | 30-59 | Franchise real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Business loans secured by real estate | 60-89
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	6,398
Loans held for investment		0
Business loans secured by real estate | 60-89 | SBA secured by real estate
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Business loans secured by real estate | 60-89 | CRE owner-occupied
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	6,398
Loans held for investment		0
Business loans secured by real estate | 60-89 | Franchise real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Business loans secured by real estate | 90+
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	4,934
Loans held for investment		5,393
Business loans secured by real estate | 90+ | SBA secured by real estate
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	83
Loans held for investment		441
Business loans secured by real estate | 90+ | CRE owner-occupied
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	4,851
Loans held for investment		4,952
Business loans secured by real estate | 90+ | Franchise real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Commercial loans
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,585,953
Loans held for investment	2,585,953	2,506,733
Commercial loans | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,164,623
Loans held for investment	2,164,623	2,103,112
Commercial loans | Franchise non-real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	409,773
Loans held for investment	409,773	392,576
Commercial loans | SBA non-real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	11,557
Loans held for investment	11,557	11,045
Commercial loans | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,580,217
Loans held for investment		2,504,453
Commercial loans | Current | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,159,494
Loans held for investment		2,101,558
Commercial loans | Current | Franchise non-real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	409,773
Loans held for investment		392,576
Commercial loans | Current | SBA non-real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	10,950
Loans held for investment		10,319
Commercial loans | 30-59
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	240
Loans held for investment		165
Commercial loans | 30-59 | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	240
Loans held for investment		92
Commercial loans | 30-59 | Franchise non-real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Commercial loans | 30-59 | SBA non-real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		73
Commercial loans | 60-89
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	135
Loans held for investment		0
Commercial loans | 60-89 | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	135
Loans held for investment		0
Commercial loans | 60-89 | Franchise non-real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Commercial loans | 60-89 | SBA non-real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Commercial loans | 90+
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	5,361
Loans held for investment		2,115
Commercial loans | 90+ | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	4,754
Loans held for investment		1,462
Commercial loans | 90+ | Franchise non-real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Commercial loans | 90+ | SBA non-real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	607
Loans held for investment		653
Retail loans
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	78,937
Loans held for investment	78,937	100,957
Retail loans | Single family residential
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	75,176
Loans held for investment	75,176	95,292
Retail loans | Consumer
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	3,761
Loans held for investment	3,761	5,665
Retail loans | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	78,935
Loans held for investment		100,957
Retail loans | Current | Single family residential
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	75,176
Loans held for investment		95,292
Retail loans | Current | Consumer
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	3,759
Loans held for investment		5,665
Retail loans | 30-59
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Retail loans | 30-59 | Single family residential
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Retail loans | 30-59 | Consumer
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Retail loans | 60-89
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2
Loans held for investment		0
Retail loans | 60-89 | Single family residential
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Retail loans | 60-89 | Consumer
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2
Loans held for investment		0
Retail loans | 90+
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Retail loans | 90+ | Single family residential
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
Retail loans | 90+ | Consumer
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	$ 0
Loans held for investment		$ 0