Loans Held for Investment - Delinquencies (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	$ 15,098,695
Loans held for investment	15,047,608	$ 14,295,897
Fair value hedging relationships	(51,087)	(5,298)
Current
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	15,062,420
Loans held for investment		14,276,402
30-59
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	6,915
Loans held for investment		1,395
60-89
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	0
Loans held for investment		0
90+
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	29,360
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	9,352,734
Loans held for investment	9,352,734	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	2,788,715
Loans held for investment	2,788,715	2,771,137
Investor loans secured by real estate | Multifamily
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	6,188,086
Loans held for investment	6,188,086	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	331,734
Loans held for investment	331,734	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	44,199
Loans held for investment	44,199	46,917
Investor loans secured by real estate | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	9,327,272
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	2,772,126
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	6,179,213
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	331,734
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	44,199
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	6,359
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	6,359
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	19,103
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	10,230
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	8,873
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	2,941,621
Loans held for investment	2,941,621	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	67,191
Loans held for investment	67,191	69,184
Business loans secured by real estate | CRE owner-occupied
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,486,747
Loans held for investment	2,486,747	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	387,683
Loans held for investment	387,683	380,381
Business loans secured by real estate | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,936,649
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	67,108
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	2,481,858
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	387,683
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	83
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	83
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	0
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	0
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	4,889
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	0
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	4,889
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	2,722,259
Loans held for investment	2,722,259	2,506,733
Commercial loans | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,295,421
Loans held for investment	2,295,421	2,103,112
Commercial loans | Franchise non-real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	415,830
Loans held for investment	415,830	392,576
Commercial loans | SBA non-real estate secured
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	11,008
Loans held for investment	11,008	11,045
Commercial loans | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	2,716,418
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	2,290,204
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	415,830
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	10,384
Loans held for investment		10,319
Commercial loans | 30-59
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	473
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	473
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	0
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	0
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	5,368
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	4,744
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	624
Loans held for investment		653
Retail loans
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	82,081
Loans held for investment	82,081	100,957
Retail loans | Single family residential
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	77,951
Loans held for investment	77,951	95,292
Retail loans | Consumer
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	4,130
Loans held for investment	4,130	5,665
Retail loans | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	82,081
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	77,951
Loans held for investment		95,292
Retail loans | Current | Consumer
Financing Receivable, Past Due [Line Items]
Loans held for investment before basis adjustment	4,130
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	0
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	0
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