Allowance for Credit Losses - Commercial Real Estate and Commercial Loan Segments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	$ 3,483,154	$ 1,862,085
Fiscal Year before Current Fiscal Year	1,875,610	3,354,750
Two Years before Current Fiscal Year	2,573,205	2,140,513
Three Years before Current Fiscal Year	1,527,156	1,729,763
Four Years before Current Fiscal Year	1,244,757	1,072,603
Prior	2,286,095	2,152,690
Revolving	989,785	912,643
Revolving Converted to Term During the Period	3,099	11,386
Total	13,982,861	13,236,433
Investor loans secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	2,346,289	1,351,350
Fiscal Year before Current Fiscal Year	1,406,768	2,386,517
Two Years before Current Fiscal Year	1,874,113	1,437,278
Three Years before Current Fiscal Year	1,026,187	988,649
Four Years before Current Fiscal Year	741,908	674,159
Prior	1,465,337	1,374,935
Revolving	10,390	12,877
Revolving Converted to Term During the Period	0	0
Total	8,870,992	8,225,765
Investor loans secured by real estate | CRE non-owner-occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	2,823,065	2,675,085
Investor loans secured by real estate | CRE non-owner-occupied | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	530,275	261,885
Fiscal Year before Current Fiscal Year	239,267	491,522
Two Years before Current Fiscal Year	392,557	431,791
Three Years before Current Fiscal Year	421,922	266,942
Four Years before Current Fiscal Year	198,651	254,527
Prior	722,951	763,101
Revolving	4,270	11,114
Revolving Converted to Term During the Period	0	0
Total	2,509,893	2,480,882
Investor loans secured by real estate | CRE non-owner-occupied | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	35,330	4,016
Fiscal Year before Current Fiscal Year	24,645	34,360
Two Years before Current Fiscal Year	23,757	5,794
Three Years before Current Fiscal Year	9,755	10,558
Four Years before Current Fiscal Year	11,088	16,961
Prior	53,696	33,734
Revolving	5,329	0
Revolving Converted to Term During the Period	0	0
Total	163,600	105,423
Investor loans secured by real estate | CRE non-owner-occupied | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	4,821	25,844
Two Years before Current Fiscal Year	50,121	11,480
Three Years before Current Fiscal Year	32,661	10,517
Four Years before Current Fiscal Year	9,933	10,782
Prior	51,511	29,598
Revolving	525	559
Revolving Converted to Term During the Period	0	0
Total	149,572	88,780
Investor loans secured by real estate | Multifamily
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	5,705,666	5,171,356
Investor loans secured by real estate | Multifamily | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	1,660,670	950,089
Fiscal Year before Current Fiscal Year	962,609	1,610,011
Two Years before Current Fiscal Year	1,316,575	878,233
Three Years before Current Fiscal Year	520,329	634,268
Four Years before Current Fiscal Year	500,815	349,549
Prior	609,731	516,452
Revolving	218	0
Revolving Converted to Term During the Period	0	0
Total	5,570,947	4,938,602
Investor loans secured by real estate | Multifamily | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	28,718	38,892
Fiscal Year before Current Fiscal Year	49,737	59,500
Two Years before Current Fiscal Year	31,988	12,181
Three Years before Current Fiscal Year	6,958	19,751
Four Years before Current Fiscal Year	1,590	10,917
Prior	8,314	13,606
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	127,305	154,847
Investor loans secured by real estate | Multifamily | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	5,059	38,663
Fiscal Year before Current Fiscal Year	0	9,963
Two Years before Current Fiscal Year	0	11,339
Three Years before Current Fiscal Year	0	12,479
Four Years before Current Fiscal Year	0	3,814
Prior	2,355	1,229
Revolving	0	420
Revolving Converted to Term During the Period	0	0
Total	7,414	77,907
Investor loans secured by real estate | Construction and land
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	292,815	321,993
Investor loans secured by real estate | Construction and land | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	56,187	55,785
Fiscal Year before Current Fiscal Year	82,557	40,860
Two Years before Current Fiscal Year	2,329	4,604
Three Years before Current Fiscal Year	991	11,238
Four Years before Current Fiscal Year	3,996	0
Prior	3,607	6,412
Revolving	48	784
Revolving Converted to Term During the Period	0	0
Total	149,715	119,683
Investor loans secured by real estate | Construction and land | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	21,654	1,123
Fiscal Year before Current Fiscal Year	11,027	41,046
Two Years before Current Fiscal Year	1,700	9,197
Three Years before Current Fiscal Year	0	3,601
Four Years before Current Fiscal Year	0	0
Prior	0	260
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	34,381	55,227
Investor loans secured by real estate | Construction and land | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	8,266	401
Fiscal Year before Current Fiscal Year	31,606	62,853
Two Years before Current Fiscal Year	47,704	59,512
Three Years before Current Fiscal Year	21,143	3,786
Four Years before Current Fiscal Year	0	20,531
Prior	0	0
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	108,719	147,083
Investor loans secured by real estate | SBA secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	49,446	57,331
Investor loans secured by real estate | SBA secured by real estate | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	130	496
Fiscal Year before Current Fiscal Year	499	10,400
Two Years before Current Fiscal Year	7,373	12,558
Three Years before Current Fiscal Year	12,428	14,497
Four Years before Current Fiscal Year	15,206	7,078
Prior	12,834	10,032
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	48,470	55,061
Investor loans secured by real estate | SBA secured by real estate | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [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	1,012
Four Years before Current Fiscal Year	0	0
Prior	0	0
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	0	1,012
Investor loans secured by real estate | SBA secured by real estate | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	0	158
Two Years before Current Fiscal Year	9	589
Three Years before Current Fiscal Year	0	0
Four Years before Current Fiscal Year	629	0
Prior	338	511
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	976	1,258
Business loans secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	737,142	344,058
Fiscal Year before Current Fiscal Year	348,383	516,400
Two Years before Current Fiscal Year	390,418	422,995
Three Years before Current Fiscal Year	285,786	446,733
Four Years before Current Fiscal Year	292,026	267,062
Prior	607,955	529,565
Revolving	4,572	14,518
Revolving Converted to Term During the Period	300	246
Total	2,666,582	2,541,577
Business loans secured by real estate | SBA secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	69,937	79,595
Business loans secured by real estate | SBA secured by real estate | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	3,789	3,253
Fiscal Year before Current Fiscal Year	2,368	7,637
Two Years before Current Fiscal Year	6,237	11,840
Three Years before Current Fiscal Year	9,605	15,069
Four Years before Current Fiscal Year	8,900	5,707
Prior	16,909	18,742
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	47,808	62,248
Business loans secured by real estate | SBA secured by real estate | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	0	0
Two Years before Current Fiscal Year	1,296	768
Three Years before Current Fiscal Year	893	989
Four Years before Current Fiscal Year	2,318	2,780
Prior	8,273	4,882
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	12,780	9,419
Business loans secured by real estate | SBA secured by real estate | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	0	0
Two Years before Current Fiscal Year	0	1,384
Three Years before Current Fiscal Year	1,326	1,987
Four Years before Current Fiscal Year	3,012	1,514
Prior	3,650	3,043
Revolving	1,361	0
Revolving Converted to Term During the Period	0	0
Total	9,349	7,928
Business loans secured by real estate | CRE owner-occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	2,242,164	2,114,050
Business loans secured by real estate | CRE owner-occupied | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	635,469	286,745
Fiscal Year before Current Fiscal Year	302,683	367,269
Two Years before Current Fiscal Year	315,267	274,512
Three Years before Current Fiscal Year	215,974	295,809
Four Years before Current Fiscal Year	201,190	202,282
Prior	499,308	422,614
Revolving	3,211	10,393
Revolving Converted to Term During the Period	300	246
Total	2,173,402	1,859,870
Business loans secured by real estate | CRE owner-occupied | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	0	8,769
Fiscal Year before Current Fiscal Year	0	42,310
Two Years before Current Fiscal Year	7,846	60,222
Three Years before Current Fiscal Year	7,573	28,421
Four Years before Current Fiscal Year	6,733	23,875
Prior	31,811	44,855
Revolving	0	3,875
Revolving Converted to Term During the Period	0	0
Total	53,963	212,327
Business loans secured by real estate | CRE owner-occupied | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	0	16,096
Two Years before Current Fiscal Year	0	5,376
Three Years before Current Fiscal Year	6,109	7,459
Four Years before Current Fiscal Year	2,972	4,263
Prior	5,718	8,409
Revolving	0	250
Revolving Converted to Term During the Period	0	0
Total	14,799	41,853
Business loans secured by real estate | Franchise real estate secured
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	354,481	347,932
Business loans secured by real estate | Franchise real estate secured | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	95,937	37,262
Fiscal Year before Current Fiscal Year	43,332	79,926
Two Years before Current Fiscal Year	55,621	65,619
Three Years before Current Fiscal Year	39,053	96,672
Four Years before Current Fiscal Year	61,591	19,046
Prior	37,696	22,927
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	333,230	321,452
Business loans secured by real estate | Franchise real estate secured | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	812	7,587
Fiscal Year before Current Fiscal Year	0	1,650
Two Years before Current Fiscal Year	4,151	3,274
Three Years before Current Fiscal Year	5,253	327
Four Years before Current Fiscal Year	5,310	5,627
Prior	4,590	4,093
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	20,116	22,558
Business loans secured by real estate | Franchise real estate secured | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	1,135	442
Fiscal Year before Current Fiscal Year	0	1,512
Two Years before Current Fiscal Year	0	0
Three Years before Current Fiscal Year	0	0
Four Years before Current Fiscal Year	0	1,968
Prior	0	0
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	1,135	3,922
Commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	379,494	155,831
Fiscal Year before Current Fiscal Year	116,911	444,000
Two Years before Current Fiscal Year	306,644	266,221
Three Years before Current Fiscal Year	213,528	280,317
Four Years before Current Fiscal Year	203,854	97,412
Prior	123,041	120,099
Revolving	948,281	854,568
Revolving Converted to Term During the Period	2,799	11,140
Total	2,294,552	2,229,588
Commercial loans | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	1,888,870	1,768,834
Commercial loans | Commercial and industrial | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	253,639	70,233
Fiscal Year before Current Fiscal Year	87,252	205,395
Two Years before Current Fiscal Year	196,671	99,178
Three Years before Current Fiscal Year	118,678	193,046
Four Years before Current Fiscal Year	128,879	36,957
Prior	69,707	62,682
Revolving	764,279	394,124
Revolving Converted to Term During the Period	2,055	5,051
Total	1,621,160	1,066,666
Commercial loans | Commercial and industrial | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	6,720	49,883
Fiscal Year before Current Fiscal Year	2,293	50,743
Two Years before Current Fiscal Year	8,012	35,813
Three Years before Current Fiscal Year	20,835	13,427
Four Years before Current Fiscal Year	27,760	12,922
Prior	8,438	13,948
Revolving	140,001	322,123
Revolving Converted to Term During the Period	4	2,469
Total	214,063	501,328
Commercial loans | Commercial and industrial | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	650	7,701
Fiscal Year before Current Fiscal Year	1,759	7,540
Two Years before Current Fiscal Year	741	29,078
Three Years before Current Fiscal Year	2,901	4,485
Four Years before Current Fiscal Year	1,143	4,574
Prior	2,376	8,350
Revolving	43,337	136,253
Revolving Converted to Term During the Period	740	2,859
Total	53,647	200,840
Commercial loans | Franchise non-real estate secured
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	392,950	444,797
Commercial loans | Franchise non-real estate secured | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	108,905	21,409
Fiscal Year before Current Fiscal Year	19,246	145,392
Two Years before Current Fiscal Year	63,233	88,171
Three Years before Current Fiscal Year	59,636	38,010
Four Years before Current Fiscal Year	22,735	21,956
Prior	15,697	23,479
Revolving	0	0
Revolving Converted to Term During the Period	0	502
Total	289,452	338,919
Commercial loans | Franchise non-real estate secured | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	9,159	6,198
Fiscal Year before Current Fiscal Year	5,708	15,754
Two Years before Current Fiscal Year	33,550	5,454
Three Years before Current Fiscal Year	5,594	8,164
Four Years before Current Fiscal Year	3,483	18,415
Prior	18,536	3,626
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	76,030	57,611
Commercial loans | Franchise non-real estate secured | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	269	0
Fiscal Year before Current Fiscal Year	0	16,836
Two Years before Current Fiscal Year	2,237	6,612
Three Years before Current Fiscal Year	4,491	18,655
Four Years before Current Fiscal Year	16,368	1,638
Prior	4,103	3,165
Revolving	0	1,361
Revolving Converted to Term During the Period	0	0
Total	27,468	48,267
Commercial loans | SBA non-real estate secured
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	12,732	15,957
Commercial loans | SBA non-real estate secured | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	152	407
Fiscal Year before Current Fiscal Year	653	2,257
Two Years before Current Fiscal Year	1,215	910
Three Years before Current Fiscal Year	633	1,078
Four Years before Current Fiscal Year	1,008	441
Prior	2,421	2,782
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	6,082	7,875
Commercial loans | SBA non-real estate secured | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	0	0
Two Years before Current Fiscal Year	209	648
Three Years before Current Fiscal Year	305	1,596
Four Years before Current Fiscal Year	2,231	169
Prior	1,137	1,652
Revolving	0	0
Revolving Converted to Term During the Period	0	259
Total	3,882	4,324
Commercial loans | SBA non-real estate secured | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	0	83
Two Years before Current Fiscal Year	776	357
Three Years before Current Fiscal Year	455	1,856
Four Years before Current Fiscal Year	247	340
Prior	626	415
Revolving	664	707
Revolving Converted to Term During the Period	0	0
Total	2,768	3,758
Commercial loans | Total commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Current Fiscal Year	379,494	155,831
Fiscal Year before Current Fiscal Year	116,911	444,000
Two Years before Current Fiscal Year	306,644	266,221
Three Years before Current Fiscal Year	213,528	280,317
Four Years before Current Fiscal Year	203,854	97,412
Prior	123,041	120,099
Revolving	948,281	854,568
Revolving Converted to Term During the Period	2,799	11,140
Total	$ 2,294,552	$ 2,229,588