Loans Receivable and Allowance for Credit Losses (Credit Risk Ratings and/or Vintage Years for Loans Held-for-Investment by Portfolio Segment) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	$ 5,896,909
2019	8,429,073
2018	5,796,044
2017	3,409,990
2016	1,712,616
Prior	3,798,982
Revolving Loans Amortized Cost Basis	7,993,253
Revolving Loans Converted to Term Loans Amortized Cost Basis	192,545
Total	37,229,412	$ 34,778,539
Commercial lending
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	4,742,649
2019	6,434,759
2018	4,088,402
2017	2,226,428
2016	1,108,642
Prior	2,585,072
Revolving Loans Amortized Cost Basis	6,718,408
Revolving Loans Converted to Term Loans Amortized Cost Basis	20,546
Total	27,924,906	25,914,252
Commercial lending \| Commercial and industrial (“C&I”)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	2,931,604
2019	2,173,071
2018	924,901
2017	359,207
2016	92,427
Prior	389,608
Revolving Loans Amortized Cost Basis	6,542,043
Revolving Loans Converted to Term Loans Amortized Cost Basis	9,830
Total	13,422,691	12,150,931
Commercial lending \| Commercial and industrial (“C&I”) \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	2,922,977
2019	2,010,048
2018	818,374
2017	328,471
2016	85,000
Prior	380,727
Revolving Loans Amortized Cost Basis	6,007,247
Revolving Loans Converted to Term Loans Amortized Cost Basis	9,830
Total	12,562,674
Commercial lending \| Commercial and industrial (“C&I”) \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	525
2019	80,449
2018	54,144
2017	22,757
2016	150
Prior	6,105
Revolving Loans Amortized Cost Basis	251,461
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	415,591
Commercial lending \| Commercial and industrial (“C&I”) \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	8,102
2019	82,574
2018	52,383
2017	7,979
2016	6,313
Prior	2,515
Revolving Loans Amortized Cost Basis	283,335
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	443,201
Commercial lending \| Commercial and industrial (“C&I”) \| Doubtful
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	964
Prior	261
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	1,225
Commercial lending \| Commercial real estate (“CRE”)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	1,271,194
2019	2,911,788
2018	2,468,368
2017	1,446,468
2016	813,052
Prior	1,809,972
Revolving Loans Amortized Cost Basis	170,556
Revolving Loans Converted to Term Loans Amortized Cost Basis	10,716
Total	10,902,114	10,278,448
Commercial lending \| Commercial real estate (“CRE”) \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	1,249,819
2019	2,859,844
2018	2,410,797
2017	1,380,086
2016	794,228
Prior	1,722,081
Revolving Loans Amortized Cost Basis	170,556
Revolving Loans Converted to Term Loans Amortized Cost Basis	10,716
Total	10,598,127
Commercial lending \| Commercial real estate (“CRE”) \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	13,072
2019	0
2018	49,860
2017	22,468
2016	1,611
Prior	45,309
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	132,320
Commercial lending \| Commercial real estate (“CRE”) \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	8,303
2019	51,944
2018	7,711
2017	43,914
2016	17,213
Prior	42,582
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	171,667
Commercial lending \| Real estate loan \| Multifamily residential
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	489,855
2019	1,066,230
2018	509,563
2017	414,771
2016	181,527
Prior	364,630
Revolving Loans Amortized Cost Basis	5,809
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	3,032,385	2,856,374
Commercial lending \| Real estate loan \| Multifamily residential \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	489,855
2019	1,045,053
2018	507,413
2017	414,771
2016	181,265
Prior	357,680
Revolving Loans Amortized Cost Basis	5,809
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	3,001,846
Commercial lending \| Real estate loan \| Multifamily residential \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	20,433
2018	0
2017	0
2016	262
Prior	1,228
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	21,923
Commercial lending \| Real estate loan \| Multifamily residential \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	744
2018	2,150
2017	0
2016	0
Prior	5,722
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	8,616
Commercial lending \| Construction and land
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	49,996
2019	283,670
2018	185,570
2017	5,982
2016	21,636
Prior	20,862
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	567,716	628,499
Commercial lending \| Construction and land \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	46,378
2019	283,670
2018	185,570
2017	5,982
2016	21,636
Prior	1,170
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	544,406
Commercial lending \| Construction and land \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	3,618
2019	0
2018	0
2017	0
2016	0
Prior	19,692
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	23,310
Commercial lending \| Total CRE
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	1,811,045
2019	4,261,688
2018	3,163,501
2017	1,867,221
2016	1,016,215
Prior	2,195,464
Revolving Loans Amortized Cost Basis	176,365
Revolving Loans Converted to Term Loans Amortized Cost Basis	10,716
Total	14,502,215	13,763,321
Consumer lending
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	1,154,260
2019	1,994,314
2018	1,707,642
2017	1,183,562
2016	603,974
Prior	1,213,910
Revolving Loans Amortized Cost Basis	1,274,845
Revolving Loans Converted to Term Loans Amortized Cost Basis	171,999
Total	9,304,506	8,864,287
Consumer lending \| Real estate loan \| Single-family residential
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	1,150,786
2019	1,989,055
2018	1,698,879
2017	1,166,652
2016	595,155
Prior	1,059,567
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	7,660,094	7,108,590
Consumer lending \| Real estate loan \| Single-family residential \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	1,150,786
2019	1,987,025
2018	1,694,022
2017	1,162,434
2016	593,501
Prior	1,047,965
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	7,635,733
Consumer lending \| Real estate loan \| Single-family residential \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	637
2018	1,601
2017	836
2016	305
Prior	1,834
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	5,213
Consumer lending \| Real estate loan \| Single-family residential \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	1,393
2018	3,256
2017	3,382
2016	1,349
Prior	9,768
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	19,148
Consumer lending \| HELOCs
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	185
2019	987
2018	5,405
2017	12,581
2016	8,819
Prior	22,515
Revolving Loans Amortized Cost Basis	1,239,460
Revolving Loans Converted to Term Loans Amortized Cost Basis	171,999
Total	1,461,951	1,472,783
Consumer lending \| HELOCs \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	185
2019	836
2018	4,417
2017	7,949
2016	7,511
Prior	18,097
Revolving Loans Amortized Cost Basis	1,239,458
Revolving Loans Converted to Term Loans Amortized Cost Basis	168,658
Total	1,447,111
Consumer lending \| HELOCs \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	200
2017	0
2016	0
Prior	380
Revolving Loans Amortized Cost Basis	2
Revolving Loans Converted to Term Loans Amortized Cost Basis	190
Total	772
Consumer lending \| HELOCs \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	151
2018	788
2017	4,632
2016	1,308
Prior	4,038
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	3,151
Total	14,068
Consumer lending \| Total residential mortgage
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	1,150,971
2019	1,990,042
2018	1,704,284
2017	1,179,233
2016	603,974
Prior	1,082,082
Revolving Loans Amortized Cost Basis	1,239,460
Revolving Loans Converted to Term Loans Amortized Cost Basis	171,999
Total	9,122,045	8,581,373
Consumer lending \| Other consumer
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	3,289
2019	4,272
2018	3,358
2017	4,329
2016	0
Prior	131,828
Revolving Loans Amortized Cost Basis	35,385
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	182,461	282,914
Consumer lending \| Other consumer \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	3,236
2019	4,272
2018	3,358
2017	1,838
2016	0
Prior	131,825
Revolving Loans Amortized Cost Basis	35,372
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	179,901
Consumer lending \| Other consumer \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	51
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	51
Consumer lending \| Other consumer \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	2
2019	0
2018	0
2017	2,491
2016	0
Prior	3
Revolving Loans Amortized Cost Basis	13
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	$ 2,509
Non-PCI Loans
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		34,555,668
Non-PCI Loans \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		33,582,886
Non-PCI Loans \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		515,702
Non-PCI Loans \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		440,105
Non-PCI Loans \| Doubtful
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		16,975
Non-PCI Loans \| Commercial lending
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		25,777,039
Non-PCI Loans \| Commercial lending \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		24,836,765
Non-PCI Loans \| Commercial lending \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		510,632
Non-PCI Loans \| Commercial lending \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		412,667
Non-PCI Loans \| Commercial lending \| Doubtful
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		16,975
Non-PCI Loans \| Commercial lending \| Commercial and industrial (“C&I”)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		12,149,121
Non-PCI Loans \| Commercial lending \| Commercial and industrial (“C&I”) \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		11,423,094
Non-PCI Loans \| Commercial lending \| Commercial and industrial (“C&I”) \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		406,543
Non-PCI Loans \| Commercial lending \| Commercial and industrial (“C&I”) \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		302,509
Non-PCI Loans \| Commercial lending \| Commercial and industrial (“C&I”) \| Doubtful
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		16,975
Non-PCI Loans \| Commercial lending \| Commercial real estate (“CRE”)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		10,165,247
Non-PCI Loans \| Commercial lending \| Commercial real estate (“CRE”) \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		10,003,749
Non-PCI Loans \| Commercial lending \| Commercial real estate (“CRE”) \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		83,683
Non-PCI Loans \| Commercial lending \| Commercial real estate (“CRE”) \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		77,815
Non-PCI Loans \| Commercial lending \| Commercial real estate (“CRE”) \| Doubtful
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		0
Non-PCI Loans \| Commercial lending \| Real estate loan \| Multifamily residential
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		2,834,212
Non-PCI Loans \| Commercial lending \| Real estate loan \| Multifamily residential \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		2,806,475
Non-PCI Loans \| Commercial lending \| Real estate loan \| Multifamily residential \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		20,406
Non-PCI Loans \| Commercial lending \| Real estate loan \| Multifamily residential \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		7,331
Non-PCI Loans \| Commercial lending \| Real estate loan \| Multifamily residential \| Doubtful
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		0
Non-PCI Loans \| Commercial lending \| Construction and land
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		628,459
Non-PCI Loans \| Commercial lending \| Construction and land \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		603,447
Non-PCI Loans \| Commercial lending \| Construction and land \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		0
Non-PCI Loans \| Commercial lending \| Construction and land \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		25,012
Non-PCI Loans \| Commercial lending \| Construction and land \| Doubtful
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		0
Non-PCI Loans \| Commercial lending \| Total CRE
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		13,627,918
Non-PCI Loans \| Commercial lending \| Total CRE \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		13,413,671
Non-PCI Loans \| Commercial lending \| Total CRE \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		104,089
Non-PCI Loans \| Commercial lending \| Total CRE \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		110,158
Non-PCI Loans \| Commercial lending \| Total CRE \| Doubtful
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		0
Non-PCI Loans \| Consumer lending
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		8,778,629
Non-PCI Loans \| Consumer lending \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		8,746,121
Non-PCI Loans \| Consumer lending \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		5,070
Non-PCI Loans \| Consumer lending \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		27,438
Non-PCI Loans \| Consumer lending \| Doubtful
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		0
Non-PCI Loans \| Consumer lending \| Real estate loan \| Single-family residential
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		7,028,979
Non-PCI Loans \| Consumer lending \| Real estate loan \| Single-family residential \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		7,012,522
Non-PCI Loans \| Consumer lending \| Real estate loan \| Single-family residential \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		2,278
Non-PCI Loans \| Consumer lending \| Real estate loan \| Single-family residential \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		14,179
Non-PCI Loans \| Consumer lending \| Real estate loan \| Single-family residential \| Doubtful
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		0
Non-PCI Loans \| Consumer lending \| HELOCs
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Total		1,466,736

Loans Receivable and Allowance for Credit Losses (Credit Risk Ratings and/or Vintage Years for Loans Held-for-Investment by Portfolio Segment) (Details) - USD ($)
$ in Thousands