Loans Held for Investment - Summary of Investments by Origination Year and Internal Risk Grading System (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	$ 52,527		$ 397,723
Fiscal year before current fiscal year	392,315		2,905,140
Two years before current fiscal year	2,845,457		3,742,197
Three years before current fiscal year	3,667,281		1,239,280
Four years before current fiscal year	1,226,955		1,546,480
Prior	3,769,566		2,395,055
Revolving	1,088,157		1,066,289
Revolving Converted to Term During the Period	2,137		26,407
Loans held for investment	13,012,071		13,289,020
Loans held for investment before basis adjustment	13,044,395		13,318,571
Current fiscal year charge off	0		132
One year before current fiscal year charge off	142		3,053
Two year before current fiscal year charge off	3,345		597
Three year before current fiscal year charge off	707		196
Four year before current fiscal year charge off	29		1,944
Prior year before current fiscal year charge off	1,841		6,534
Revolving charge off	465		6,390
Revolving Converted to Term During the Period charge off	0		503
Total	6,529	$ 3,664	19,349
Basis adjustment associated with fair value hedge
Financing Receivable, Credit Quality Indicator [Line Items]
Loans held for investment before basis adjustment	13,044,395		13,318,571
Basis adjustment associated with fair value hedge	32,324		29,551
Investor loans secured by real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	35,496		310,500
Fiscal year before current fiscal year	286,148		1,986,752
Two years before current fiscal year	1,962,118		2,655,460
Three years before current fiscal year	2,613,042		920,238
Four years before current fiscal year	914,328		1,145,258
Prior	2,579,026		1,557,818
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment	8,390,158		8,576,026
Loans held for investment before basis adjustment	8,390,158		8,576,026
Current fiscal year charge off	0		0
One year before current fiscal year charge off	0		0
Two year before current fiscal year charge off	0		217
Three year before current fiscal year charge off	0		0
Four year before current fiscal year charge off	0		1,582
Prior year before current fiscal year charge off	1,180		3,653
Revolving charge off	0		0
Revolving Converted to Term During the Period charge off	0		0
Total	1,180		5,452
Investor loans secured by real estate | CRE non-owner-occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Loans held for investment	2,309,252		2,421,772
Loans held for investment before basis adjustment	2,309,252		2,421,772
Total	927	66
Investor loans secured by real estate | CRE non-owner-occupied | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	25,930		71,452
Fiscal year before current fiscal year	39,449		482,045
Two years before current fiscal year	456,670		549,828
Three years before current fiscal year	530,041		192,399
Four years before current fiscal year	174,446		315,139
Prior	1,044,831		795,856
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	2,271,367		2,406,719
Investor loans secured by real estate | CRE non-owner-occupied | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		0
Fiscal year before current fiscal year	0		3,811
Two years before current fiscal year	4,190		2,530
Three years before current fiscal year	2,509		0
Four years before current fiscal year	0		0
Prior	0		625
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	6,699		6,966
Investor loans secured by real estate | CRE non-owner-occupied | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		0
Fiscal year before current fiscal year	0		412
Two years before current fiscal year	2,785		0
Three years before current fiscal year	0		0
Four years before current fiscal year	16,209		0
Prior	12,192		7,675
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	31,186		8,087
Investor loans secured by real estate | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Loans held for investment	5,558,966		5,645,310
Loans held for investment before basis adjustment	5,558,966		5,645,310
Total	0	217
Investor loans secured by real estate | Multifamily | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	2,332		179,055
Fiscal year before current fiscal year	183,941		1,184,329
Two years before current fiscal year	1,172,758		2,008,126
Three years before current fiscal year	1,965,579		725,123
Four years before current fiscal year	708,447		822,411
Prior	1,478,920		714,638
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	5,511,977		5,633,682
Investor loans secured by real estate | Multifamily | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		0
Fiscal year before current fiscal year	0		0
Two years before current fiscal year	0		0
Three years before current fiscal year	18,303		0
Four years before current fiscal year	0		0
Prior	11,576		11,628
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	29,879		11,628
Investor loans secured by real estate | Multifamily | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0
Fiscal year before current fiscal year	0
Two years before current fiscal year	0
Three years before current fiscal year	4,603
Four years before current fiscal year	12,507
Prior	0
Revolving	0
Revolving Converted to Term During the Period	0
Loans held for investment before basis adjustment	17,110
Investor loans secured by real estate | Construction and land
Financing Receivable, Credit Quality Indicator [Line Items]
Loans held for investment	486,734		472,544
Loans held for investment before basis adjustment	486,734		472,544
Total	0	0
Investor loans secured by real estate | Construction and land | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	7,234		59,993
Fiscal year before current fiscal year	62,758		309,677
Two years before current fiscal year	319,264		94,845
Three years before current fiscal year	91,445		2,223
Four years before current fiscal year	2,226		2,368
Prior	3,376		3,438
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	486,303		472,544
Investor loans secured by real estate | Construction and land | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0
Fiscal year before current fiscal year	0
Two years before current fiscal year	0
Three years before current fiscal year	431
Four years before current fiscal year	0
Prior	0
Revolving	0
Revolving Converted to Term During the Period	0
Loans held for investment before basis adjustment	431
Investor loans secured by real estate | SBA secured by real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans held for investment	35,206		36,400
Loans held for investment before basis adjustment	35,206		36,400
Total	253	0
Investor loans secured by real estate | SBA secured by real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		0
Fiscal year before current fiscal year	0		6,478
Two years before current fiscal year	6,451		0
Three years before current fiscal year	0		493
Four years before current fiscal year	493		4,804
Prior	20,541		16,496
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	27,485		28,271
Investor loans secured by real estate | SBA secured by real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		0
Fiscal year before current fiscal year	0		0
Two years before current fiscal year	0		131
Three years before current fiscal year	131		0
Four years before current fiscal year	0		536
Prior	7,590		7,462
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	7,721		8,129
Business loans secured by real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	10,535		31,465
Fiscal year before current fiscal year	31,824		632,163
Two years before current fiscal year	612,935		797,090
Three years before current fiscal year	780,161		257,990
Four years before current fiscal year	254,793		243,137
Prior	801,560		583,825
Revolving	918		919
Revolving Converted to Term During the Period	0		0
Loans held for investment	2,492,726		2,546,589
Loans held for investment before basis adjustment	2,492,726		2,546,589
Current fiscal year charge off	0		0
One year before current fiscal year charge off	93		0
Two year before current fiscal year charge off	3,345		318
Three year before current fiscal year charge off	581		191
Four year before current fiscal year charge off	0		0
Prior year before current fiscal year charge off	645		1,861
Revolving charge off	0		0
Revolving Converted to Term During the Period charge off	0		0
Total	4,664		2,370
Business loans secured by real estate | SBA secured by real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans held for investment	48,426		50,741
Loans held for investment before basis adjustment	48,426		50,741
Total	0	0
Business loans secured by real estate | SBA secured by real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		113
Fiscal year before current fiscal year	112		9,334
Two years before current fiscal year	9,827		7,634
Three years before current fiscal year	7,350		1,979
Four years before current fiscal year	1,949		4,109
Prior	24,669		22,417
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	43,907		45,586
Business loans secured by real estate | SBA secured by real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		0
Fiscal year before current fiscal year	0		536
Two years before current fiscal year	0		0
Three years before current fiscal year	0		0
Four years before current fiscal year	0		0
Prior	82		83
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	82		619
Business loans secured by real estate | SBA secured by real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		0
Fiscal year before current fiscal year	0		0
Two years before current fiscal year	0		0
Three years before current fiscal year	0		0
Four years before current fiscal year	0		0
Prior	4,437		4,536
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	4,437		4,536
Business loans secured by real estate | CRE owner-occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Loans held for investment	2,149,362		2,191,334
Loans held for investment before basis adjustment	2,149,362		2,191,334
Total	4,452	2,163
Business loans secured by real estate | CRE owner-occupied | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	9,310		19,014
Fiscal year before current fiscal year	21,215		543,413
Two years before current fiscal year	541,542		660,967
Three years before current fiscal year	615,237		224,333
Four years before current fiscal year	217,548		211,283
Prior	651,272		458,975
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	2,056,124		2,117,985
Business loans secured by real estate | CRE owner-occupied | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		0
Fiscal year before current fiscal year	0		16,535
Two years before current fiscal year	6,349		0
Three years before current fiscal year	36,625		476
Four years before current fiscal year	472		4,775
Prior	4,863		11,775
Revolving	918		919
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	49,227		34,480
Business loans secured by real estate | CRE owner-occupied | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		0
Fiscal year before current fiscal year	0		15,539
Two years before current fiscal year	9,815		2,162
Three years before current fiscal year	0		5,505
Four years before current fiscal year	9,455		3,873
Prior	24,741		11,790
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	44,011		38,869
Business loans secured by real estate | Franchise real estate secured
Financing Receivable, Credit Quality Indicator [Line Items]
Loans held for investment	294,938		304,514
Loans held for investment before basis adjustment	294,938		304,514
Total	212	0
Business loans secured by real estate | Franchise real estate secured | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,225		10,580
Fiscal year before current fiscal year	10,497		39,239
Two years before current fiscal year	41,473		124,424
Three years before current fiscal year	120,949		25,697
Four years before current fiscal year	25,369		15,731
Prior	88,080		72,342
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	287,593		288,013
Business loans secured by real estate | Franchise real estate secured | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		1,758
Fiscal year before current fiscal year	0		3,603
Two years before current fiscal year	0		1,903
Three years before current fiscal year	0		0
Four years before current fiscal year	0		795
Prior	1,597		1,615
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	1,597		9,674
Business loans secured by real estate | Franchise real estate secured | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		0
Fiscal year before current fiscal year	0		3,964
Two years before current fiscal year	3,929		0
Three years before current fiscal year	0		0
Four years before current fiscal year	0		2,571
Prior	1,819		292
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	5,748		6,827
Commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	6,496		55,738
Fiscal year before current fiscal year	74,323		286,225
Two years before current fiscal year	270,404		289,644
Three years before current fiscal year	274,076		60,876
Four years before current fiscal year	57,661		158,080
Prior	345,267		208,520
Revolving	1,056,964		1,035,765
Revolving Converted to Term During the Period	2,137		26,407
Loans held for investment	2,087,328		2,121,255
Loans held for investment before basis adjustment	2,087,328		2,121,255
Current fiscal year charge off	0		132
One year before current fiscal year charge off	49		3,053
Two year before current fiscal year charge off	0		62
Three year before current fiscal year charge off	126		5
Four year before current fiscal year charge off	29		362
Prior year before current fiscal year charge off	16		37
Revolving charge off	465		6,387
Revolving Converted to Term During the Period charge off	0		503
Total	685		10,541
Commercial loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans held for investment	1,774,487		1,790,608
Loans held for investment before basis adjustment	1,774,487		1,790,608
Total	585	1,123
Commercial loans | Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	6,427		46,765
Fiscal year before current fiscal year	49,636		172,987
Two years before current fiscal year	156,868		160,275
Three years before current fiscal year	148,942		40,988
Four years before current fiscal year	38,675		110,526
Prior	244,163		146,310
Revolving	975,215		966,733
Revolving Converted to Term During the Period	825		6,518
Loans held for investment before basis adjustment	1,620,751		1,651,102
Commercial loans | Commercial and industrial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		239
Fiscal year before current fiscal year	1,027		23,242
Two years before current fiscal year	22,364		12,270
Three years before current fiscal year	13,948		367
Four years before current fiscal year	335		16
Prior	2,162		2,139
Revolving	34,604		42,570
Revolving Converted to Term During the Period	1,312		407
Loans held for investment before basis adjustment	75,752		81,250
Commercial loans | Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		425
Fiscal year before current fiscal year	14,289		8,052
Two years before current fiscal year	8,052		2,689
Three years before current fiscal year	2,735		588
Four years before current fiscal year	406		173
Prior	1,248		1,138
Revolving	47,145		26,462
Revolving Converted to Term During the Period	0		14,187
Loans held for investment before basis adjustment	73,875		53,714
Commercial loans | Commercial and industrial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0
Fiscal year before current fiscal year	0
Two years before current fiscal year	4,109
Three years before current fiscal year	0
Four years before current fiscal year	0
Prior	0
Revolving	0
Revolving Converted to Term During the Period	0
Loans held for investment before basis adjustment	4,109
Commercial loans | Franchise non-real estate secured
Financing Receivable, Credit Quality Indicator [Line Items]
Loans held for investment	301,895		319,721
Loans held for investment before basis adjustment	301,895		319,721
Total	100	0
Commercial loans | Franchise non-real estate secured | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	69		6,801
Fiscal year before current fiscal year	7,789		74,441
Two years before current fiscal year	72,481		112,112
Three years before current fiscal year	107,807		16,355
Four years before current fiscal year	15,807		34,770
Prior	81,601		53,957
Revolving	0		0
Revolving Converted to Term During the Period	0		753
Loans held for investment before basis adjustment	285,554		299,189
Commercial loans | Franchise non-real estate secured | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		433
Fiscal year before current fiscal year	0		845
Two years before current fiscal year	0		1,633
Three years before current fiscal year	0		0
Four years before current fiscal year	0		627
Prior	648		692
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	648		4,230
Commercial loans | Franchise non-real estate secured | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		0
Fiscal year before current fiscal year	0		1,646
Two years before current fiscal year	1,600		322
Three years before current fiscal year	306		2,324
Four years before current fiscal year	2,189		10,451
Prior	11,598		1,559
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	15,693		16,302
Commercial loans | SBA non-real estate secured
Financing Receivable, Credit Quality Indicator [Line Items]
Loans held for investment	10,946		10,926
Loans held for investment before basis adjustment	10,946		10,926
Total	0	0
Commercial loans | SBA non-real estate secured | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		1,075
Fiscal year before current fiscal year	1,582		4,485
Two years before current fiscal year	4,415		343
Three years before current fiscal year	338		113
Four years before current fiscal year	111		1,464
Prior	3,701		2,490
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	10,147		9,970
Commercial loans | SBA non-real estate secured | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		0
Fiscal year before current fiscal year	0		527
Two years before current fiscal year	515		0
Three years before current fiscal year	0		141
Four years before current fiscal year	138		53
Prior	146		235
Revolving	0		0
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	799		956
Commercial loans | Consumer | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year			0
Fiscal year before current fiscal year			0
Two years before current fiscal year			0
Three years before current fiscal year			0
Four years before current fiscal year			0
Prior			0
Revolving			0
Revolving Converted to Term During the Period			4,542
Loans held for investment before basis adjustment			4,542
Retail loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		20
Fiscal year before current fiscal year	20		0
Two years before current fiscal year	0		3
Three years before current fiscal year	2		176
Four years before current fiscal year	173		5
Prior	43,713		44,892
Revolving	30,275		29,605
Revolving Converted to Term During the Period	0		0
Loans held for investment	74,183		74,701
Loans held for investment before basis adjustment	74,183		74,701
Current fiscal year charge off	0		0
One year before current fiscal year charge off	0		0
Two year before current fiscal year charge off	0		0
Three year before current fiscal year charge off	0		0
Four year before current fiscal year charge off	0		0
Prior year before current fiscal year charge off	0		983
Revolving charge off	0		3
Revolving Converted to Term During the Period charge off	0		0
Total	0		986
Retail loans | Single family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Loans held for investment	72,353		72,752
Loans held for investment before basis adjustment	72,353		72,752
Total	0	90
Retail loans | Single family residential | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		20
Fiscal year before current fiscal year	20		0
Two years before current fiscal year	0		0
Three years before current fiscal year	0		167
Four years before current fiscal year	165		0
Prior	43,288		44,104
Revolving	28,880		28,461
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	72,353		72,752
Retail loans | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans held for investment	1,830		1,949
Loans held for investment before basis adjustment	1,830		1,949
Total	0	$ 5
Retail loans | Consumer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0		0
Fiscal year before current fiscal year	0		0
Two years before current fiscal year	0		3
Three years before current fiscal year	2		9
Four years before current fiscal year	8		5
Prior	425		788
Revolving	1,395		1,144
Revolving Converted to Term During the Period	0		0
Loans held for investment before basis adjustment	$ 1,830		$ 1,949