Allowance for Loan Losses - Commercial Real Estate and Commercial Loan Segments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	$ 393,833
2019	1,582,645
2018	1,501,216
2017	1,375,311
2016	950,920
Prior	1,950,704
Revolving	997,131
Revolving Converted to Term During the Period	3,109
Total	8,754,869	$ 8,722,311
Investor loans secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	212,035
2019	819,651
2018	850,689
2017	669,837
2016	505,863
Prior	1,033,973
Revolving	13,022
Revolving Converted to Term During the Period	0
Total	4,105,070	4,153,084
Investor loans secured by real estate | Commercial real estate (“CRE”) non-owner-occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	2,040,198	2,070,141
Investor loans secured by real estate | Commercial real estate (“CRE”) non-owner-occupied | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	104,083
2019	373,078
2018	365,350
2017	282,641
2016	200,867
Prior	629,141
Revolving	11,644
Revolving Converted to Term During the Period	0
Total	1,966,804
Investor loans secured by real estate | Commercial real estate (“CRE”) non-owner-occupied | 5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	8,928
2018	16,401
2017	19,982
2016	6,318
Prior	5,364
Revolving	0
Revolving Converted to Term During the Period	0
Total	56,993
Investor loans secured by real estate | Commercial real estate (“CRE”) non-owner-occupied | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	0
2018	318
2017	356
2016	0
Prior	15,727
Revolving	0
Revolving Converted to Term During the Period	0
Total	16,401
Investor loans secured by real estate | Multifamily
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	1,625,682	1,575,726
Investor loans secured by real estate | Multifamily | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	99,379
2019	268,267
2018	308,116
2017	241,432
2016	291,126
Prior	356,870
Revolving	987
Revolving Converted to Term During the Period	0
Total	1,566,177
Investor loans secured by real estate | Multifamily | 5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	5,829
2019	40,102
2018	3,522
2017	506
2016	0
Prior	4,263
Revolving	0
Revolving Converted to Term During the Period	0
Total	54,222
Investor loans secured by real estate | Multifamily | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	0
2018	3,824
2017	0
2016	0
Prior	1,459
Revolving	0
Revolving Converted to Term During the Period	0
Total	5,283
Investor loans secured by real estate | Construction and land
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	377,525	438,786
Investor loans secured by real estate | Construction and land | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	2,250
2019	62,553
2018	14,444
2017	12,823
2016	0
Prior	7,408
Revolving	391
Revolving Converted to Term During the Period	0
Total	99,869
Investor loans secured by real estate | Construction and land | 5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	26,376
2018	21,927
2017	40,704
2016	0
Prior	298
Revolving	0
Revolving Converted to Term During the Period	0
Total	89,305
Investor loans secured by real estate | Construction and land | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	29,621
2018	102,969
2017	54,505
2016	0
Prior	1,256
Revolving	0
Revolving Converted to Term During the Period	0
Total	188,351
Investor loans secured by real estate | SBA secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	61,665	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	494
2019	10,726
2018	12,158
2017	16,888
2016	7,160
Prior	11,664
Revolving	0
Revolving Converted to Term During the Period	0
Total	59,090
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	1,660
2017	0
2016	0
Prior	523
Revolving	0
Revolving Converted to Term During the Period	0
Total	2,183
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	0
2017	0
2016	392
Prior	0
Revolving	0
Revolving Converted to Term During the Period	0
Total	392
Business loans secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	136,092
2019	410,425
2018	398,865
2017	449,016
2016	313,700
Prior	628,168
Revolving	6,434
Revolving Converted to Term During the Period	0
Total	2,342,700	2,288,175
Business loans secured by real estate | SBA secured by real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	83,640	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	2,109
2019	7,723
2018	13,559
2017	16,143
2016	8,948
Prior	23,564
Revolving	364
Revolving Converted to Term During the Period	0
Total	72,410
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	694
2017	2,260
2016	2,430
Prior	2,780
Revolving	0
Revolving Converted to Term During the Period	0
Total	8,164
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	1,033
2016	413
Prior	1,620
Revolving	0
Revolving Converted to Term During the Period	0
Total	3,066
Business loans secured by real estate | CRE owner-occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	1,887,632	1,846,554
Business loans secured by real estate | CRE owner-occupied | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	114,657
2019	296,223
2018	274,727
2017	303,164
2016	244,460
Prior	515,875
Revolving	5,573
Revolving Converted to Term During the Period	0
Total	1,754,679
Business loans secured by real estate | CRE owner-occupied | 5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	18,905
2018	29,663
2017	16,248
2016	23,617
Prior	31,941
Revolving	247
Revolving Converted to Term During the Period	0
Total	120,621
Business loans secured by real estate | CRE owner-occupied | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	0
2018	3,635
2017	965
2016	2,180
Prior	5,302
Revolving	250
Revolving Converted to Term During the Period	0
Total	12,332
Business loans secured by real estate | Franchise real estate secured
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	371,428	353,240
Business loans secured by real estate | Franchise real estate secured | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	19,326
2019	78,086
2018	74,790
2017	105,669
2016	30,643
Prior	38,631
Revolving	0
Revolving Converted to Term During the Period	0
Total	347,145
Business loans secured by real estate | Franchise real estate secured | 5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	1,575
2018	1,069
2017	3,534
2016	1,009
Prior	7,553
Revolving	0
Revolving Converted to Term During the Period	0
Total	14,740
Business loans secured by real estate | Franchise real estate secured | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	7,913
2018	728
2017	0
2016	0
Prior	902
Revolving	0
Revolving Converted to Term During the Period	0
Total	9,543
Commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	42,151
2019	341,291
2018	233,029
2017	201,482
2016	92,772
Prior	176,139
Revolving	933,054
Revolving Converted to Term During the Period	3,109
Total	2,023,027	1,975,053
Commercial loans | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	1,458,969	1,393,270
Commercial loans | Commercial and industrial | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	31,625
2019	114,904
2018	94,899
2017	67,070
2016	34,540
Prior	110,090
Revolving	881,734
Revolving Converted to Term During the Period	1,204
Total	1,336,066
Commercial loans | Commercial and industrial | 5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	10,607
2018	7,471
2017	38,578
2016	2,603
Prior	6,021
Revolving	27,259
Revolving Converted to Term During the Period	370
Total	92,909
Commercial loans | Commercial and industrial | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	524
2018	2,769
2017	869
2016	1,915
Prior	3,027
Revolving	19,640
Revolving Converted to Term During the Period	1,250
Total	29,994
Commercial loans | Franchise non-real estate secured
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	547,793	564,357
Commercial loans | Franchise non-real estate secured | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	9,938
2019	210,415
2018	121,918
2017	77,413
2016	48,552
Prior	44,294
Revolving	2,062
Revolving Converted to Term During the Period	0
Total	514,592
Commercial loans | Franchise non-real estate secured | 5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	323
2019	2,370
2018	4,036
2017	1,977
2016	4,174
Prior	3,430
Revolving	0
Revolving Converted to Term During the Period	0
Total	16,310
Commercial loans | Franchise non-real estate secured | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	0
2018	0
2017	13,056
2016	0
Prior	3,835
Revolving	0
Revolving Converted to Term During the Period	0
Total	16,891
Commercial loans | SBA non-real estate secured
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	16,265	$ 17,426
Commercial loans | SBA non-real estate secured | 0% - 5.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	265
2019	2,383
2018	1,326
2017	2,258
2016	601
Prior	3,503
Revolving	1,572
Revolving Converted to Term During the Period	285
Total	12,193
Commercial loans | SBA non-real estate secured | 5.00% - 10.00%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	0
2018	469
2017	0
2016	387
Prior	230
Revolving	0
Revolving Converted to Term During the Period	0
Total	1,086
Commercial loans | SBA non-real estate secured | Greater than 10%
Financing Receivable, Allowance for Credit Loss [Line Items]
2020	0
2019	88
2018	141
2017	261
2016	0
Prior	1,709
Revolving	787
Revolving Converted to Term During the Period	0
Total	$ 2,986