Allowance for Credit Losses - Commercial Real Estate and Commercial Loan Segments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	$ 2,183,956
2019	3,628,848
2018	2,540,813
2017	1,998,126
2016	1,281,491
Prior	2,541,780
Revolving	901,170
Revolving Converted to Term During the Period	6,700
Total	15,082,884	$ 8,722,311
Investor loans secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	692,143
2019	2,473,310
2018	1,661,597
2017	1,175,829
2016	802,350
Prior	1,607,953
Revolving	12,975
Revolving Converted to Term During the Period	0
Total	8,426,157	4,153,084
Investor loans secured by real estate | CRE non-owner-occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	2,783,692	2,070,141
Investor loans secured by real estate | CRE non-owner-occupied | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	153,133
2019	561,104
2018	474,139
2017	258,886
2016	279,780
Prior	793,398
Revolving	10,924
Revolving Converted to Term During the Period	0
Total	2,531,364
Investor loans secured by real estate | CRE non-owner-occupied | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	2,897
2018	8,428
2017	86,660
2016	37,621
Prior	39,947
Revolving	0
Revolving Converted to Term During the Period	0
Total	175,553
Investor loans secured by real estate | CRE non-owner-occupied | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	2,296
2019	3,988
2018	322
2017	14,155
2016	2,585
Prior	52,870
Revolving	559
Revolving Converted to Term During the Period	0
Total	76,775
Investor loans secured by real estate | Multifamily
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	5,225,557	1,575,726
Investor loans secured by real estate | Multifamily | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	520,782
2019	1,723,731
2018	991,561
2017	746,855
2016	460,328
Prior	678,741
Revolving	1,031
Revolving Converted to Term During the Period	0
Total	5,123,029
Investor loans secured by real estate | Multifamily | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	1,599
2019	17,431
2018	8,692
2017	2,176
2016	4,098
Prior	8,906
Revolving	0
Revolving Converted to Term During the Period	0
Total	42,902
Investor loans secured by real estate | Multifamily | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	12,607
2018	9,794
2017	12,545
2016	10,409
Prior	14,271
Revolving	0
Revolving Converted to Term During the Period	0
Total	59,626
Investor loans secured by real estate | Construction and land
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	357,426	438,786
Investor loans secured by real estate | Construction and land | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	13,838
2019	32,921
2018	4,296
2017	20,357
2016	0
Prior	6,919
Revolving	66
Revolving Converted to Term During the Period	0
Total	78,397
Investor loans secured by real estate | Construction and land | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	40,785
2018	21,154
2017	3,275
2016	0
Prior	0
Revolving	395
Revolving Converted to Term During the Period	0
Total	65,609
Investor loans secured by real estate | Construction and land | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	67,142
2018	129,990
2017	14,739
2016	0
Prior	1,549
Revolving	0
Revolving Converted to Term During the Period	0
Total	213,420
Investor loans secured by real estate | SBA secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	59,482	68,431
Investor loans secured by real estate | SBA secured by real estate | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	495
2019	10,704
2018	12,115
2017	16,181
2016	7,135
Prior	11,352
Revolving	0
Revolving Converted to Term During the Period	0
Total	57,982
Investor loans secured by real estate | SBA secured by real estate | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	0
2018	512
2017	0
2016	0
Prior	0
Revolving	0
Revolving Converted to Term During the Period	0
Total	512
Investor loans secured by real estate | SBA secured by real estate | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	0
2018	594
2017	0
2016	394
Prior	0
Revolving	0
Revolving Converted to Term During the Period	0
Total	988
Business loans secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	240,336
2019	548,159
2018	443,266
2017	453,579
2016	310,433
Prior	619,080
Revolving	5,490
Revolving Converted to Term During the Period	0
Total	2,620,343	2,288,175
Business loans secured by real estate | SBA secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	85,542	88,381
Business loans secured by real estate | SBA secured by real estate | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	1,905
2019	7,693
2018	13,476
2017	16,611
2016	8,547
Prior	24,605
Revolving	365
Revolving Converted to Term During the Period	0
Total	73,202
Business loans secured by real estate | SBA secured by real estate | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	0
2018	683
2017	1,699
2016	2,306
Prior	3,416
Revolving	0
Revolving Converted to Term During the Period	0
Total	8,104
Business loans secured by real estate | SBA secured by real estate | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	0
2018	0
2017	914
2016	148
Prior	3,174
Revolving	0
Revolving Converted to Term During the Period	0
Total	4,236
Business loans secured by real estate | CRE owner-occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	2,170,154	1,846,554
Business loans secured by real estate | CRE owner-occupied | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	211,860
2019	402,474
2018	309,907
2017	304,611
2016	234,139
Prior	488,345
Revolving	3,124
Revolving Converted to Term During the Period	0
Total	1,954,460
Business loans secured by real estate | CRE owner-occupied | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	186
2019	33,118
2018	35,922
2017	22,510
2016	26,918
Prior	42,552
Revolving	1,504
Revolving Converted to Term During the Period	0
Total	162,710
Business loans secured by real estate | CRE owner-occupied | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	5,979
2019	16,066
2018	7,086
2017	3,386
2016	6,797
Prior	13,173
Revolving	497
Revolving Converted to Term During the Period	0
Total	52,984
Business loans secured by real estate | Franchise real estate secured
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	364,647	353,240
Business loans secured by real estate | Franchise real estate secured | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	18,724
2019	86,263
2018	74,832
2017	95,221
2016	28,550
Prior	42,831
Revolving	0
Revolving Converted to Term During the Period	0
Total	346,421
Business loans secured by real estate | Franchise real estate secured | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	754
2019	0
2018	632
2017	8,627
2016	3,028
Prior	101
Revolving	0
Revolving Converted to Term During the Period	0
Total	13,142
Business loans secured by real estate | Franchise real estate secured | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	928
2019	2,545
2018	728
2017	0
2016	0
Prior	883
Revolving	0
Revolving Converted to Term During the Period	0
Total	5,084
Commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	1,246,542
2019	597,779
2018	419,527
2017	315,688
2016	130,311
Prior	166,605
Revolving	841,753
Revolving Converted to Term During the Period	6,700
Total	3,724,905	1,975,053
Commercial loans | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	2,051,313	1,393,270
Commercial loans | Commercial and industrial | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	91,538
2019	376,850
2018	268,429
2017	211,610
2016	58,496
Prior	94,984
Revolving	508,985
Revolving Converted to Term During the Period	1,593
Total	1,612,485
Commercial loans | Commercial and industrial | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	9,735
2019	11,741
2018	24,030
2017	11,639
2016	14,449
Prior	8,862
Revolving	271,951
Revolving Converted to Term During the Period	547
Total	352,954
Commercial loans | Commercial and industrial | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	5,496
2019	339
2018	3,625
2017	1,007
2016	7,121
Prior	9,415
Revolving	57,848
Revolving Converted to Term During the Period	1,023
Total	85,874
Commercial loans | Franchise non-real estate secured
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	523,755	564,357
Commercial loans | Franchise non-real estate secured | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	9,535
2019	197,360
2018	117,509
2017	69,287
2016	46,925
Prior	40,305
Revolving	1,476
Revolving Converted to Term During the Period	0
Total	482,397
Commercial loans | Franchise non-real estate secured | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	812
2019	6,619
2018	3,593
2017	9,290
2016	2,382
Prior	4,704
Revolving	729
Revolving Converted to Term During the Period	0
Total	28,129
Commercial loans | Franchise non-real estate secured | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	2,443
2018	514
2017	7,737
2016	0
Prior	2,535
Revolving	0
Revolving Converted to Term During the Period	0
Total	13,229
Commercial loans | SBA non-real estate secured
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	21,057	$ 17,426
Commercial loans | SBA non-real estate secured | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	646
2019	2,341
2018	1,301
2017	2,517
2016	571
Prior	3,842
Revolving	0
Revolving Converted to Term During the Period	3,537
Total	14,755
Commercial loans | SBA non-real estate secured | >5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	0
2018	132
2017	1,745
2016	367
Prior	439
Revolving	0
Revolving Converted to Term During the Period	0
Total	2,683
Commercial loans | SBA non-real estate secured | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	86
2018	394
2017	856
2016	0
Prior	1,519
Revolving	764
Revolving Converted to Term During the Period	0
Total	3,619
Commercial loans | Total commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	117,762
2019	597,779
2018	419,527
2017	315,688
2016	130,311
Prior	166,605
Revolving	841,753
Revolving Converted to Term During the Period	6,700
Total	$ 2,596,125