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	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	$ 2,919,900
2019	9,072,212
2018	5,649,484
2017	3,467,167
2016	1,720,010
Prior	4,122,520
Revolving Loans Amortized Cost Basis	8,777,087
Revolving Loans Converted to Term Loans Amortized Cost Basis	165,013
Total	35,893,393	$ 34,778,539
Commercial lending
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	2,303,898
2019	7,023,041
2018	3,863,376
2017	2,231,082
2016	1,083,761
Prior	2,780,698
Revolving Loans Amortized Cost Basis	7,475,104
Revolving Loans Converted to Term Loans Amortized Cost Basis	20,856
Total	26,781,816	25,914,252
Commercial lending \| Commercial and industrial (“C&I”)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	909,755
2019	2,500,457
2018	874,576
2017	450,484
2016	109,571
Prior	424,011
Revolving Loans Amortized Cost Basis	7,311,829
Revolving Loans Converted to Term Loans Amortized Cost Basis	10,081
Total	12,590,764	12,150,931
Commercial lending \| Commercial and industrial (“C&I”) \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	884,043
2019	2,320,726
2018	830,428
2017	381,798
2016	94,032
Prior	411,215
Revolving Loans Amortized Cost Basis	6,945,982
Revolving Loans Converted to Term Loans Amortized Cost Basis	10,081
Total	11,878,305
Commercial lending \| Commercial and industrial (“C&I”) \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	21,388
2019	98,629
2018	16,948
2017	27,701
2016	1,064
Prior	10,600
Revolving Loans Amortized Cost Basis	218,835
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	395,165
Commercial lending \| Commercial and industrial (“C&I”) \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	4,324
2019	65,448
2018	27,200
2017	40,985
2016	13,431
Prior	2,196
Revolving Loans Amortized Cost Basis	147,012
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	300,596
Commercial lending \| Commercial and industrial (“C&I”) \| Doubtful
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	15,654
2018	0
2017	0
2016	1,044
Prior	0
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	16,698
Commercial lending \| Commercial real estate (“CRE”)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	1,032,360
2019	3,090,101
2018	2,337,211
2017	1,356,185
2016	740,968
Prior	1,956,753
Revolving Loans Amortized Cost Basis	157,889
Revolving Loans Converted to Term Loans Amortized Cost Basis	10,775
Total	10,682,242	10,278,448
Commercial lending \| Commercial real estate (“CRE”) \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	1,023,184
2019	2,994,402
2018	2,319,358
2017	1,317,389
2016	739,774
Prior	1,926,748
Revolving Loans Amortized Cost Basis	157,889
Revolving Loans Converted to Term Loans Amortized Cost Basis	10,775
Total	10,489,519
Commercial lending \| Commercial real estate (“CRE”) \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	3,636
2019	66,004
2018	15,438
2017	19,896
2016	674
Prior	10,518
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	116,166
Commercial lending \| Commercial real estate (“CRE”) \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	5,540
2019	29,695
2018	2,415
2017	18,900
2016	520
Prior	19,487
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	76,557
Commercial lending \| Real estate loan \| Multifamily residential
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	293,032
2019	1,112,425
2018	491,742
2017	408,783
2016	212,174
Prior	379,059
Revolving Loans Amortized Cost Basis	5,386
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	2,902,601	2,856,374
Commercial lending \| Real estate loan \| Multifamily residential \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	293,032
2019	1,091,261
2018	489,564
2017	408,783
2016	212,174
Prior	372,554
Revolving Loans Amortized Cost Basis	5,386
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	2,872,754
Commercial lending \| Real estate loan \| Multifamily residential \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	21,164
2018	1,893
2017	0
2016	0
Prior	521
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	23,578
Commercial lending \| Real estate loan \| Multifamily residential \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	285
2017	0
2016	0
Prior	5,984
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	6,269
Commercial lending \| Construction and land
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	68,751
2019	320,058
2018	159,847
2017	15,630
2016	21,048
Prior	20,875
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	606,209	628,499
Commercial lending \| Construction and land \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	67,143
2019	316,396
2018	159,847
2017	15,630
2016	21,048
Prior	1,183
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	581,247
Commercial lending \| Construction and land \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	1,608
2019	3,662
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	24,962
Commercial lending \| Total CRE
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	1,394,143
2019	4,522,584
2018	2,988,800
2017	1,780,598
2016	974,190
Prior	2,356,687
Revolving Loans Amortized Cost Basis	163,275
Revolving Loans Converted to Term Loans Amortized Cost Basis	10,775
Total	14,191,052	13,763,321
Consumer lending
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	616,002
2019	2,049,171
2018	1,786,108
2017	1,236,085
2016	636,249
Prior	1,341,822
Revolving Loans Amortized Cost Basis	1,301,983
Revolving Loans Converted to Term Loans Amortized Cost Basis	144,157
Total	9,111,577	8,864,287
Consumer lending \| Real estate loan \| Single-family residential
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	612,040
2019	2,044,581
2018	1,779,300
2017	1,223,118
2016	628,396
Prior	1,116,288
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	7,403,723	7,108,590
Consumer lending \| Real estate loan \| Single-family residential \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	612,040
2019	2,043,504
2018	1,775,928
2017	1,218,685
2016	624,427
Prior	1,099,351
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	7,373,935
Consumer lending \| Real estate loan \| Single-family residential \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	238
2018	1,639
2017	1,253
2016	2,811
Prior	6,796
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	12,737
Consumer lending \| Real estate loan \| Single-family residential \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	839
2018	1,733
2017	3,180
2016	1,158
Prior	10,141
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	17,051
Consumer lending \| HELOCs
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	150
2018	4,171
2017	8,591
2016	7,835
Prior	26,543
Revolving Loans Amortized Cost Basis	1,261,415
Revolving Loans Converted to Term Loans Amortized Cost Basis	144,157
Total	1,452,862	1,472,783
Consumer lending \| HELOCs \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	3,182
2017	5,980
2016	6,525
Prior	19,809
Revolving Loans Amortized Cost Basis	1,260,844
Revolving Loans Converted to Term Loans Amortized Cost Basis	142,090
Total	1,438,430
Consumer lending \| HELOCs \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	700
2017	0
2016	165
Prior	1,945
Revolving Loans Amortized Cost Basis	571
Revolving Loans Converted to Term Loans Amortized Cost Basis	605
Total	3,986
Consumer lending \| HELOCs \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	150
2018	289
2017	2,611
2016	1,145
Prior	4,789
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	1,462
Total	10,446
Consumer lending \| Total residential mortgage
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	612,040
2019	2,044,731
2018	1,783,471
2017	1,231,709
2016	636,231
Prior	1,142,831
Revolving Loans Amortized Cost Basis	1,261,415
Revolving Loans Converted to Term Loans Amortized Cost Basis	144,157
Total	8,856,585	8,581,373
Consumer lending \| Other consumer
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	3,962
2019	4,440
2018	2,637
2017	4,376
2016	18
Prior	198,991
Revolving Loans Amortized Cost Basis	40,568
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	254,992	282,914
Consumer lending \| Other consumer \| Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	3,951
2019	4,440
2018	2,637
2017	1,885
2016	18
Prior	198,988
Revolving Loans Amortized Cost Basis	40,556
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	252,475
Consumer lending \| Other consumer \| Special Mention
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	11
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	11
Consumer lending \| Other consumer \| Substandard
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	2,491
2016	0
Prior	3
Revolving Loans Amortized Cost Basis	12
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	$ 2,506
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