Allowance for Credit Losses - Commercial Real Estate and Commercial Loan Segments (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Current fiscal year	$ 1,932,994	$ 1,862,085
Fiscal year before current fiscal year	1,830,360	3,354,750
Two years before current fiscal year	2,963,529	2,140,513
Three years before current fiscal year	1,819,329	1,729,763
Four years before current fiscal year	1,507,457	1,072,603
Prior	2,649,725	2,152,690
Revolving	889,352	912,643
Revolving Converted to Term During the Period	1,852	11,386
Total	13,594,598	13,236,433
Investor loans secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Current fiscal year	1,365,536	1,351,350
Fiscal year before current fiscal year	1,350,055	2,386,517
Two years before current fiscal year	2,137,775	1,437,278
Three years before current fiscal year	1,249,591	988,649
Four years before current fiscal year	870,189	674,159
Prior	1,715,122	1,374,935
Revolving	12,160	12,877
Revolving Converted to Term During the Period	0	0
Total	8,700,428	8,225,765
Investor loans secured by real estate | CRE non-owner-occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	2,810,233	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	301,013	261,885
Fiscal year before current fiscal year	239,654	491,522
Two years before current fiscal year	425,062	431,791
Three years before current fiscal year	440,854	266,942
Four years before current fiscal year	210,727	254,527
Prior	884,807	763,101
Revolving	4,652	11,114
Revolving Converted to Term During the Period	0	0
Total	2,506,769	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	0	4,016
Fiscal year before current fiscal year	23,774	34,360
Two years before current fiscal year	25,621	5,794
Three years before current fiscal year	17,921	10,558
Four years before current fiscal year	20,269	16,961
Prior	47,036	33,734
Revolving	5,328	0
Revolving Converted to Term During the Period	0	0
Total	139,949	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	4,218	25,844
Two years before current fiscal year	68,748	11,480
Three years before current fiscal year	33,118	10,517
Four years before current fiscal year	41,911	10,782
Prior	14,983	29,598
Revolving	537	559
Revolving Converted to Term During the Period	0	0
Total	163,515	88,780
Investor loans secured by real estate | Multifamily
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	5,539,464	5,171,356
Investor loans secured by real estate | Multifamily | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current fiscal year	1,004,852	950,089
Fiscal year before current fiscal year	934,432	1,610,011
Two years before current fiscal year	1,478,289	878,233
Three years before current fiscal year	684,846	634,268
Four years before current fiscal year	558,666	349,549
Prior	713,963	516,452
Revolving	1,643	0
Revolving Converted to Term During the Period	0	0
Total	5,376,691	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	22,931	38,892
Fiscal year before current fiscal year	49,688	59,500
Two years before current fiscal year	27,569	12,181
Three years before current fiscal year	15,354	19,751
Four years before current fiscal year	0	10,917
Prior	7,226	13,606
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	122,768	154,847
Investor loans secured by real estate | Multifamily | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current fiscal year	0	38,663
Fiscal year before current fiscal year	0	9,963
Two years before current fiscal year	10,739	11,339
Three years before current fiscal year	9,687	12,479
Four years before current fiscal year	12,419	3,814
Prior	7,160	1,229
Revolving	0	420
Revolving Converted to Term During the Period	0	0
Total	40,005	77,907
Investor loans secured by real estate | Construction and land
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	297,728	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	17,062	55,785
Fiscal year before current fiscal year	78,153	40,860
Two years before current fiscal year	21,725	4,604
Three years before current fiscal year	370	11,238
Four years before current fiscal year	8,321	0
Prior	4,651	6,412
Revolving	0	784
Revolving Converted to Term During the Period	0	0
Total	130,282	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	18,948	1,123
Fiscal year before current fiscal year	16,774	41,046
Two years before current fiscal year	7,211	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	42,933	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	730	401
Fiscal year before current fiscal year	2,862	62,853
Two years before current fiscal year	64,249	59,512
Three years before current fiscal year	34,964	3,786
Four years before current fiscal year	444	20,531
Prior	21,264	0
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	124,513	147,083
Investor loans secured by real estate | SBA secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	53,003	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	0	496
Fiscal year before current fiscal year	500	10,400
Two years before current fiscal year	8,460	12,558
Three years before current fiscal year	12,477	14,497
Four years before current fiscal year	17,432	7,078
Prior	13,694	10,032
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	52,563	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	102	589
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	338	511
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	440	1,258
Business loans secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Current fiscal year	338,745	344,058
Fiscal year before current fiscal year	330,353	516,400
Two years before current fiscal year	440,622	422,995
Three years before current fiscal year	345,111	446,733
Four years before current fiscal year	381,622	267,062
Prior	680,837	529,565
Revolving	3,053	14,518
Revolving Converted to Term During the Period	0	246
Total	2,520,343	2,541,577
Business loans secured by real estate | SBA secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	72,923	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	2,502	3,253
Fiscal year before current fiscal year	3,423	7,637
Two years before current fiscal year	7,492	11,840
Three years before current fiscal year	9,903	15,069
Four years before current fiscal year	10,132	5,707
Prior	18,318	18,742
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	51,770	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	70	768
Three years before current fiscal year	1,495	989
Four years before current fiscal year	2,532	2,780
Prior	8,972	4,882
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	13,069	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	1,336	1,987
Four years before current fiscal year	2,172	1,514
Prior	4,576	3,043
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	8,084	7,928
Business loans secured by real estate | CRE owner-occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	2,089,300	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	276,707	286,745
Fiscal year before current fiscal year	281,668	367,269
Two years before current fiscal year	347,620	274,512
Three years before current fiscal year	262,455	295,809
Four years before current fiscal year	269,367	202,282
Prior	558,473	422,614
Revolving	3,052	10,393
Revolving Converted to Term During the Period	0	246
Total	1,999,342	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	13,628	60,222
Three years before current fiscal year	9,092	28,421
Four years before current fiscal year	11,854	23,875
Prior	37,540	44,855
Revolving	1	3,875
Revolving Converted to Term During the Period	0	0
Total	72,115	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	6,151	7,459
Four years before current fiscal year	5,874	4,263
Prior	5,818	8,409
Revolving	0	250
Revolving Converted to Term During the Period	0	0
Total	17,843	41,853
Business loans secured by real estate | Franchise real estate secured
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	358,120	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	59,007	37,262
Fiscal year before current fiscal year	36,149	79,926
Two years before current fiscal year	71,812	65,619
Three years before current fiscal year	50,663	96,672
Four years before current fiscal year	78,597	19,046
Prior	43,345	22,927
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	339,573	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	239	7,587
Fiscal year before current fiscal year	7,558	1,650
Two years before current fiscal year	0	3,274
Three years before current fiscal year	4,016	327
Four years before current fiscal year	1,094	5,627
Prior	3,795	4,093
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	16,702	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	290	442
Fiscal year before current fiscal year	1,555	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	1,845	3,922
Commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Current fiscal year	215,357	155,831
Fiscal year before current fiscal year	143,142	444,000
Two years before current fiscal year	382,538	266,221
Three years before current fiscal year	222,333	280,317
Four years before current fiscal year	246,838	97,412
Prior	149,643	120,099
Revolving	848,656	854,568
Revolving Converted to Term During the Period	1,852	11,140
Total	2,210,359	2,229,588
Commercial loans | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	1,795,144	1,768,834
Commercial loans | Commercial and industrial | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current fiscal year	135,825	70,233
Fiscal year before current fiscal year	105,221	205,395
Two years before current fiscal year	232,476	99,178
Three years before current fiscal year	102,539	193,046
Four years before current fiscal year	155,592	36,957
Prior	84,339	62,682
Revolving	626,121	394,124
Revolving Converted to Term During the Period	1,852	5,051
Total	1,443,965	1,066,666
Commercial loans | Commercial and industrial | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current fiscal year	22,487	49,883
Fiscal year before current fiscal year	6,242	50,743
Two years before current fiscal year	10,701	35,813
Three years before current fiscal year	18,922	13,427
Four years before current fiscal year	33,612	12,922
Prior	7,924	13,948
Revolving	162,253	322,123
Revolving Converted to Term During the Period	0	2,469
Total	262,141	501,328
Commercial loans | Commercial and industrial | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current fiscal year	0	7,701
Fiscal year before current fiscal year	4,944	7,540
Two years before current fiscal year	1,533	29,078
Three years before current fiscal year	18,386	4,485
Four years before current fiscal year	564	4,574
Prior	5,518	8,350
Revolving	58,093	136,253
Revolving Converted to Term During the Period	0	2,859
Total	89,038	200,840
Commercial loans | Franchise non-real estate secured
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	401,315	444,797
Commercial loans | Franchise non-real estate secured | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current fiscal year	56,293	21,409
Fiscal year before current fiscal year	20,482	145,392
Two years before current fiscal year	94,203	88,171
Three years before current fiscal year	67,224	38,010
Four years before current fiscal year	30,596	21,956
Prior	24,823	23,479
Revolving	0	0
Revolving Converted to Term During the Period	0	502
Total	293,621	338,919
Commercial loans | Franchise non-real estate secured | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current fiscal year	599	6,198
Fiscal year before current fiscal year	5,840	15,754
Two years before current fiscal year	39,085	5,454
Three years before current fiscal year	8,783	8,164
Four years before current fiscal year	4,910	18,415
Prior	19,921	3,626
Revolving	151	0
Revolving Converted to Term During the Period	0	0
Total	79,289	57,611
Commercial loans | Franchise 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	16,836
Two years before current fiscal year	2,293	6,612
Three years before current fiscal year	4,665	18,655
Four years before current fiscal year	17,749	1,638
Prior	2,337	3,165
Revolving	1,361	1,361
Revolving Converted to Term During the Period	0	0
Total	28,405	48,267
Commercial loans | SBA non-real estate secured
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	13,900	15,957
Commercial loans | SBA non-real estate secured | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
Current fiscal year	153	407
Fiscal year before current fiscal year	413	2,257
Two years before current fiscal year	2,167	910
Three years before current fiscal year	990	1,078
Four years before current fiscal year	1,159	441
Prior	3,385	2,782
Revolving	0	0
Revolving Converted to Term During the Period	0	0
Total	8,267	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	0	648
Three years before current fiscal year	479	1,596
Four years before current fiscal year	2,398	169
Prior	657	1,652
Revolving	0	0
Revolving Converted to Term During the Period	0	259
Total	3,534	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	80	357
Three years before current fiscal year	345	1,856
Four years before current fiscal year	258	340
Prior	739	415
Revolving	677	707
Revolving Converted to Term During the Period	0	0
Total	2,099	3,758
Commercial loans | Total commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Current fiscal year	215,357	155,831
Fiscal year before current fiscal year	143,142	444,000
Two years before current fiscal year	382,538	266,221
Three years before current fiscal year	222,333	280,317
Four years before current fiscal year	246,838	97,412
Prior	149,643	120,099
Revolving	848,656	854,568
Revolving Converted to Term During the Period	1,852	11,140
Total	$ 2,210,359	$ 2,229,588