Loans Held for Investment - Internal Risk Grading System under ASC 326 (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	$ 1,074,728	$ 4,696,852
Fiscal Year before Current Fiscal Year	4,657,598	1,736,838
Two Years before Current Fiscal Year	1,608,350	2,322,876
Three Years before Current Fiscal Year	2,154,680	1,254,797
Four Years before Current Fiscal Year	1,121,305	1,143,567
Prior	2,873,255	2,014,563
Revolving	1,241,092	1,121,488
Revolving Converted to Term During the Period	2,747	4,916
Total	14,733,755	14,295,897
Investor loans secured by real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	690,589	3,088,930
Fiscal Year before Current Fiscal Year	3,083,122	1,320,289
Two Years before Current Fiscal Year	1,208,893	1,681,360
Three Years before Current Fiscal Year	1,546,339	865,841
Four Years before Current Fiscal Year	775,029	717,023
Prior	1,848,076	1,304,033
Revolving	10,140	10,152
Revolving Converted to Term During the Period	0	0
Total	9,162,188	8,987,628
Investor loans secured by real estate | CRE non-owner-occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,774,650	2,771,137
Investor loans secured by real estate | CRE non-owner-occupied | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	176,426	708,560
Fiscal Year before Current Fiscal Year	670,633	269,944
Two Years before Current Fiscal Year	257,088	393,097
Three Years before Current Fiscal Year	403,482	387,923
Four Years before Current Fiscal Year	348,314	218,388
Prior	870,240	730,736
Revolving	9,354	9,353
Revolving Converted to Term During the Period	0	0
Total	2,735,537	2,718,001
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	0
Two Years before Current Fiscal Year	0	16,166
Three Years before Current Fiscal Year	0	7,682
Four Years before Current Fiscal Year	7,633	0
Prior	2,245	0
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	9,878	23,848
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	0
Two Years before Current Fiscal Year	0	25,777
Three Years before Current Fiscal Year	25,780	0
Four Years before Current Fiscal Year	0	0
Prior	2,955	2,998
Revolving	500	513
Revolving Converted to Term During the Period	0	0
Total	29,235	29,288
Investor loans secured by real estate | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Total	6,041,085	5,891,934
Investor loans secured by real estate | Multifamily | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	465,994	2,260,708
Fiscal Year before Current Fiscal Year	2,279,374	952,127
Two Years before Current Fiscal Year	871,658	1,199,505
Three Years before Current Fiscal Year	1,082,386	444,904
Four Years before Current Fiscal Year	399,926	479,029
Prior	940,701	554,067
Revolving	286	286
Revolving Converted to Term During the Period	0	0
Total	6,040,325	5,890,626
Investor loans secured by real estate | Multifamily | 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	543
Four Years before Current Fiscal Year	0	0
Prior	760	765
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	760	1,308
Investor loans secured by real estate | Construction and land
Financing Receivable, Credit Quality Indicator [Line Items]
Total	303,811	277,640
Investor loans secured by real estate | Construction and land | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	46,203	119,532
Fiscal Year before Current Fiscal Year	132,985	97,721
Two Years before Current Fiscal Year	79,651	40,556
Three Years before Current Fiscal Year	28,556	12,415
Four Years before Current Fiscal Year	9,027	3,857
Prior	7,389	3,559
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	303,811	277,640
Investor loans secured by real estate | SBA secured by real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total	42,642	46,917
Investor loans secured by real estate | SBA secured by real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	1,966	130
Fiscal Year before Current Fiscal Year	130	497
Two Years before Current Fiscal Year	496	6,259
Three Years before Current Fiscal Year	6,135	9,074
Four Years before Current Fiscal Year	6,847	12,070
Prior	18,215	9,198
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	33,789	37,228
Investor loans secured by real estate | SBA secured by real estate | 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		957
Four Years before Current Fiscal Year		0
Prior		544
Revolving		0
Revolving Converted to Term During the Period		0
Total		1,501
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	0
Three Years before Current Fiscal Year	0	2,343
Four Years before Current Fiscal Year	3,282	3,679
Prior	5,571	2,166
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	8,853	8,188
Business loans secured by real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	281,024	1,015,804
Fiscal Year before Current Fiscal Year	994,405	312,168
Two Years before Current Fiscal Year	306,308	352,224
Three Years before Current Fiscal Year	342,773	218,944
Four Years before Current Fiscal Year	192,883	259,808
Prior	722,605	533,240
Revolving	4,719	8,099
Revolving Converted to Term During the Period	0	292
Total	2,844,717	2,700,579
Business loans secured by real estate | CRE non-owner-occupied | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year		1,015,804
Fiscal Year before Current Fiscal Year		312,168
Two Years before Current Fiscal Year		352,224
Three Years before Current Fiscal Year		218,944
Four Years before Current Fiscal Year		259,808
Prior		533,240
Revolving		8,099
Revolving Converted to Term During the Period		292
Total		2,700,579
Business loans secured by real estate | SBA secured by real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total	68,466	69,184
Business loans secured by real estate | SBA secured by real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	6,107	6,379
Fiscal Year before Current Fiscal Year	7,452	2,364
Two Years before Current Fiscal Year	2,357	7,331
Three Years before Current Fiscal Year	7,133	9,125
Four Years before Current Fiscal Year	4,760	10,734
Prior	32,189	24,627
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	59,998	60,560
Business loans secured by real estate | SBA secured by real estate | 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		0
Four Years before Current Fiscal Year		0
Prior		62
Revolving		0
Revolving Converted to Term During the Period		0
Total		62
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	2,062
Four Years before Current Fiscal Year	1,888	2,690
Prior	6,580	3,810
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	8,468	8,562
Business loans secured by real estate | CRE owner-occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,391,984	2,251,014
Business loans secured by real estate | CRE owner-occupied | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	250,202	853,044
Fiscal Year before Current Fiscal Year	830,646	273,469
Two Years before Current Fiscal Year	263,304	287,249
Three Years before Current Fiscal Year	279,071	161,636
Four Years before Current Fiscal Year	143,848	187,130
Prior	597,055	464,271
Revolving	4,719	6,738
Revolving Converted to Term During the Period	0	292
Total	2,368,845	2,233,829
Business loans secured by real estate | CRE owner-occupied | 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	0
Four Years before Current Fiscal Year	764
Prior	0
Revolving	0
Revolving Converted to Term During the Period	0
Total	764
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	0
Two Years before Current Fiscal Year	4,673	2,553
Three Years before Current Fiscal Year	2,516	6,074
Four Years before Current Fiscal Year	5,140	2,966
Prior	10,046	5,592
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	22,375	17,185
Business loans secured by real estate | Franchise real estate secured
Financing Receivable, Credit Quality Indicator [Line Items]
Total	384,267	380,381
Business loans secured by real estate | Franchise real estate secured | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	24,715	156,381
Fiscal Year before Current Fiscal Year	156,307	36,335
Two Years before Current Fiscal Year	35,974	55,091
Three Years before Current Fiscal Year	54,053	40,047
Four Years before Current Fiscal Year	36,483	56,288
Prior	76,735	34,878
Revolving	0	1,361
Revolving Converted to Term During the Period	0	0
Total	384,267	380,381
Commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	103,115	591,794
Fiscal Year before Current Fiscal Year	579,752	104,142
Two Years before Current Fiscal Year	92,930	289,238
Three Years before Current Fiscal Year	265,527	169,961
Four Years before Current Fiscal Year	153,352	164,717
Prior	245,541	107,053
Revolving	1,198,751	1,075,204
Revolving Converted to Term During the Period	2,747	4,624
Total	2,641,715	2,506,733
Commercial loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,242,632	2,103,112
Commercial loans | Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	77,907	425,683
Fiscal Year before Current Fiscal Year	417,259	79,635
Two Years before Current Fiscal Year	68,739	200,234
Three Years before Current Fiscal Year	185,229	117,471
Four Years before Current Fiscal Year	105,770	123,345
Prior	180,774	70,789
Revolving	1,171,092	1,032,053
Revolving Converted to Term During the Period	2,747	3,371
Total	2,209,517	2,052,581
Commercial loans | Commercial and industrial | 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	339	146
Three Years before Current Fiscal Year	0	0
Four Years before Current Fiscal Year	0	0
Prior	142	152
Revolving	530	14,814
Revolving Converted to Term During the Period	0	178
Total	1,011	15,290
Commercial loans | Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	963	1,772
Fiscal Year before Current Fiscal Year	2,317	0
Two Years before Current Fiscal Year	0	14
Three Years before Current Fiscal Year	12	2,683
Four Years before Current Fiscal Year	1,365	863
Prior	1,621	1,150
Revolving	25,826	27,684
Revolving Converted to Term During the Period	0	1,075
Total	32,104	35,241
Commercial loans | Franchise non-real estate secured
Financing Receivable, Credit Quality Indicator [Line Items]
Total	388,322	392,576
Commercial loans | Franchise non-real estate secured | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	23,582	163,865
Fiscal Year before Current Fiscal Year	159,709	23,943
Two Years before Current Fiscal Year	23,309	85,206
Three Years before Current Fiscal Year	76,734	45,061
Four Years before Current Fiscal Year	41,700	23,672
Prior	43,597	31,163
Revolving	661	0
Revolving Converted to Term During the Period	0	0
Total	369,292	372,910
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	0
Two Years before Current Fiscal Year	0	1,589
Three Years before Current Fiscal Year	1,550	3,627
Four Years before Current Fiscal Year	3,517	13,346
Prior	13,963	1,104
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	19,030	19,666
Commercial loans | SBA non-real estate secured
Financing Receivable, Credit Quality Indicator [Line Items]
Total	10,761	11,045
Commercial loans | SBA non-real estate secured | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	663	474
Fiscal Year before Current Fiscal Year	467	564
Two Years before Current Fiscal Year	543	1,292
Three Years before Current Fiscal Year	1,861	666
Four Years before Current Fiscal Year	756	2,806
Prior	4,752	2,148
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	9,042	7,950
Commercial loans | SBA non-real estate secured | 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	681
Three Years before Current Fiscal Year	66	114
Four Years before Current Fiscal Year	0	0
Prior	0	0
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	66	795
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	0
Two Years before Current Fiscal Year	0	76
Three Years before Current Fiscal Year	75	339
Four Years before Current Fiscal Year	244	685
Prior	692	547
Revolving	642	653
Revolving Converted to Term During the Period	0	0
Total	1,653	2,300
Retail loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	0	324
Fiscal Year before Current Fiscal Year	319	239
Two Years before Current Fiscal Year	219	54
Three Years before Current Fiscal Year	41	51
Four Years before Current Fiscal Year	41	2,019
Prior	57,033	70,237
Revolving	27,482	28,033
Revolving Converted to Term During the Period	0	0
Total	85,135	100,957
Retail loans | Single family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total	79,978	95,292
Retail loans | Single family residential | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	0	313
Fiscal Year before Current Fiscal Year	309	211
Two Years before Current Fiscal Year	194	0
Three Years before Current Fiscal Year	0	32
Four Years before Current Fiscal Year	31	2,008
Prior	55,677	68,759
Revolving	23,721	23,920
Revolving Converted to Term During the Period	0	0
Total	79,932	95,243
Retail loans | Single family residential | 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	46	49
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	46	49
Retail loans | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total	5,157	5,665
Retail loans | Consumer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	0	11
Fiscal Year before Current Fiscal Year	10	28
Two Years before Current Fiscal Year	25	49
Three Years before Current Fiscal Year	37	19
Four Years before Current Fiscal Year	10	11
Prior	1,310	1,394
Revolving	3,761	4,113
Revolving Converted to Term During the Period	0	0
Total	5,153	5,625
Retail loans | Consumer | 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	5
Three Years before Current Fiscal Year	4	0
Four Years before Current Fiscal Year	0	0
Prior	0	35
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	$ 4	$ 40