Loans Receivable and Allowance for Credit Losses (Aging Analysis on Loans Held-for-Investment) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	$ 84,992
Total Nonaccrual Loans	236,494
Current Accruing Loans	37,115,643
Financing Receivable, before Allowance for Credit Loss, Total	37,437,129	$ 34,778,539
Accruing Loans 30-59  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	31,960
Accruing Loans 60-89  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	53,032
Nonaccrual Loans Less Than 90  Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	115,539
Nonaccrual Loans 90 or More Days  Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	120,955
Commercial lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	65,652
Total Nonaccrual Loans	205,710
Current Accruing Loans	27,707,330
Financing Receivable, before Allowance for Credit Loss, Total	27,978,692	25,914,252
Commercial lending | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	53,143
Total Nonaccrual Loans	145,986
Current Accruing Loans	13,105,895
Financing Receivable, before Allowance for Credit Loss, Total	13,305,024	12,150,931
Commercial lending | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	8,646
Total Nonaccrual Loans	55,996
Current Accruing Loans	10,973,345
Financing Receivable, before Allowance for Credit Loss, Total	11,037,987	10,278,448
Commercial lending | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	3,863
Total Nonaccrual Loans	3,728
Current Accruing Loans	3,049,683
Financing Receivable, before Allowance for Credit Loss, Total	3,057,274	2,856,374
Commercial lending | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0
Total Nonaccrual Loans	0
Current Accruing Loans	578,407
Financing Receivable, before Allowance for Credit Loss, Total	578,407	628,499
Commercial lending | Total CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	12,509
Total Nonaccrual Loans	59,724
Current Accruing Loans	14,601,435
Financing Receivable, before Allowance for Credit Loss, Total	14,673,668	13,763,321
Commercial lending | Accruing Loans 30-59  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	18,174
Commercial lending | Accruing Loans 30-59  Days Past Due | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	6,024
Commercial lending | Accruing Loans 30-59  Days Past Due | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	8,646
Commercial lending | Accruing Loans 30-59  Days Past Due | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	3,504
Commercial lending | Accruing Loans 30-59  Days Past Due | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0
Commercial lending | Accruing Loans 30-59  Days Past Due | Total CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	12,150
Commercial lending | Accruing Loans 60-89  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	47,478
Commercial lending | Accruing Loans 60-89  Days Past Due | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	47,119
Commercial lending | Accruing Loans 60-89  Days Past Due | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0
Commercial lending | Accruing Loans 60-89  Days Past Due | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	359
Commercial lending | Accruing Loans 60-89  Days Past Due | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0
Commercial lending | Accruing Loans 60-89  Days Past Due | Total CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	359
Commercial lending | Nonaccrual Loans Less Than 90  Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	113,810
Commercial lending | Nonaccrual Loans Less Than 90  Days Past Due | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	110,068
Commercial lending | Nonaccrual Loans Less Than 90  Days Past Due | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	1,338
Commercial lending | Nonaccrual Loans Less Than 90  Days Past Due | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	2,404
Commercial lending | Nonaccrual Loans Less Than 90  Days Past Due | Construction and land
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	0
Commercial lending | Nonaccrual Loans Less Than 90  Days Past Due | Total CRE
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	3,742
Commercial lending | Nonaccrual Loans 90 or More Days  Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	91,900
Commercial lending | Nonaccrual Loans 90 or More Days  Past Due | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	35,918
Commercial lending | Nonaccrual Loans 90 or More Days  Past Due | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	54,658
Commercial lending | Nonaccrual Loans 90 or More Days  Past Due | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	1,324
Commercial lending | Nonaccrual Loans 90 or More Days  Past Due | Construction and land
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	0
Commercial lending | Nonaccrual Loans 90 or More Days  Past Due | Total CRE
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	55,982
Consumer lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	19,340
Total Nonaccrual Loans	30,784
Current Accruing Loans	9,408,313
Financing Receivable, before Allowance for Credit Loss, Total	9,458,437	8,864,287
Consumer lending | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	13,987
Total Nonaccrual Loans	15,894
Current Accruing Loans	7,755,878
Financing Receivable, before Allowance for Credit Loss, Total	7,785,759	7,108,590
Consumer lending | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	4,678
Total Nonaccrual Loans	12,395
Current Accruing Loans	1,497,315
Financing Receivable, before Allowance for Credit Loss, Total	1,514,388	1,472,783
Consumer lending | Total residential mortgage
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	18,665
Total Nonaccrual Loans	28,289
Current Accruing Loans	9,253,193
Financing Receivable, before Allowance for Credit Loss, Total	9,300,147	8,581,373
Consumer lending | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	675
Total Nonaccrual Loans	2,495
Current Accruing Loans	155,120
Financing Receivable, before Allowance for Credit Loss, Total	158,290	282,914
Consumer lending | Accruing Loans 30-59  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	13,786
Consumer lending | Accruing Loans 30-59  Days Past Due | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	9,076
Consumer lending | Accruing Loans 30-59  Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	4,038
Consumer lending | Accruing Loans 30-59  Days Past Due | Total residential mortgage
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	13,114
Consumer lending | Accruing Loans 30-59  Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	672
Consumer lending | Accruing Loans 60-89  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	5,554
Consumer lending | Accruing Loans 60-89  Days Past Due | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	4,911
Consumer lending | Accruing Loans 60-89  Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	640
Consumer lending | Accruing Loans 60-89  Days Past Due | Total residential mortgage
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	5,551
Consumer lending | Accruing Loans 60-89  Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	3
Consumer lending | Nonaccrual Loans Less Than 90  Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	1,729
Consumer lending | Nonaccrual Loans Less Than 90  Days Past Due | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	1,149
Consumer lending | Nonaccrual Loans Less Than 90  Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	580
Consumer lending | Nonaccrual Loans Less Than 90  Days Past Due | Total residential mortgage
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	1,729
Consumer lending | Nonaccrual Loans Less Than 90  Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	0
Consumer lending | Nonaccrual Loans 90 or More Days  Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	29,055
Consumer lending | Nonaccrual Loans 90 or More Days  Past Due | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	14,745
Consumer lending | Nonaccrual Loans 90 or More Days  Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	11,815
Consumer lending | Nonaccrual Loans 90 or More Days  Past Due | Total residential mortgage
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	26,560
Consumer lending | Nonaccrual Loans 90 or More Days  Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	$ 2,495
Non-PCI Loans
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		101,283
Total Nonaccrual Loans		120,219
Current Accruing Loans		34,334,166
Financing Receivable, before Allowance for Credit Loss, Total		34,555,668
Non-PCI Loans | Accruing Loans 30-59  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		73,871
Non-PCI Loans | Accruing Loans 60-89  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		27,412
Non-PCI Loans | Nonaccrual Loans Less Than 90  Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		35,570
Non-PCI Loans | Nonaccrual Loans 90 or More Days  Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		84,649
Non-PCI Loans | Commercial lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		73,691
Total Nonaccrual Loans		92,095
Current Accruing Loans		25,611,253
Financing Receivable, before Allowance for Credit Loss, Total		25,777,039
Non-PCI Loans | Commercial lending | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		48,155
Total Nonaccrual Loans		74,835
Current Accruing Loans		12,026,131
Financing Receivable, before Allowance for Credit Loss, Total		12,149,121
Non-PCI Loans | Commercial lending | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		24,807
Total Nonaccrual Loans		16,441
Current Accruing Loans		10,123,999
Financing Receivable, before Allowance for Credit Loss, Total		10,165,247
Non-PCI Loans | Commercial lending | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		729
Total Nonaccrual Loans		819
Current Accruing Loans		2,832,664
Financing Receivable, before Allowance for Credit Loss, Total		2,834,212
Non-PCI Loans | Commercial lending | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		0
Total Nonaccrual Loans		0
Current Accruing Loans		628,459
Financing Receivable, before Allowance for Credit Loss, Total		628,459
Non-PCI Loans | Commercial lending | Total CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		25,536
Total Nonaccrual Loans		17,260
Current Accruing Loans		13,585,122
Financing Receivable, before Allowance for Credit Loss, Total		13,627,918
Non-PCI Loans | Commercial lending | Accruing Loans 30-59  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		54,149
Non-PCI Loans | Commercial lending | Accruing Loans 30-59  Days Past Due | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		31,121
Non-PCI Loans | Commercial lending | Accruing Loans 30-59  Days Past Due | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		22,830
Non-PCI Loans | Commercial lending | Accruing Loans 30-59  Days Past Due | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		198
Non-PCI Loans | Commercial lending | Accruing Loans 30-59  Days Past Due | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		0
Non-PCI Loans | Commercial lending | Accruing Loans 30-59  Days Past Due | Total CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		23,028
Non-PCI Loans | Commercial lending | Accruing Loans 60-89  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		19,542
Non-PCI Loans | Commercial lending | Accruing Loans 60-89  Days Past Due | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		17,034
Non-PCI Loans | Commercial lending | Accruing Loans 60-89  Days Past Due | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		1,977
Non-PCI Loans | Commercial lending | Accruing Loans 60-89  Days Past Due | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		531
Non-PCI Loans | Commercial lending | Accruing Loans 60-89  Days Past Due | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		0
Non-PCI Loans | Commercial lending | Accruing Loans 60-89  Days Past Due | Total CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		2,508
Non-PCI Loans | Commercial lending | Nonaccrual Loans Less Than 90  Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		32,158
Non-PCI Loans | Commercial lending | Nonaccrual Loans Less Than 90  Days Past Due | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		31,084
Non-PCI Loans | Commercial lending | Nonaccrual Loans Less Than 90  Days Past Due | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		540
Non-PCI Loans | Commercial lending | Nonaccrual Loans Less Than 90  Days Past Due | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		534
Non-PCI Loans | Commercial lending | Nonaccrual Loans Less Than 90  Days Past Due | Construction and land
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		0
Non-PCI Loans | Commercial lending | Nonaccrual Loans Less Than 90  Days Past Due | Total CRE
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		1,074
Non-PCI Loans | Commercial lending | Nonaccrual Loans 90 or More Days  Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		59,937
Non-PCI Loans | Commercial lending | Nonaccrual Loans 90 or More Days  Past Due | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		43,751
Non-PCI Loans | Commercial lending | Nonaccrual Loans 90 or More Days  Past Due | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		15,901
Non-PCI Loans | Commercial lending | Nonaccrual Loans 90 or More Days  Past Due | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		285
Non-PCI Loans | Commercial lending | Nonaccrual Loans 90 or More Days  Past Due | Construction and land
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		0
Non-PCI Loans | Commercial lending | Nonaccrual Loans 90 or More Days  Past Due | Total CRE
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		16,186
Non-PCI Loans | Consumer lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		27,592
Total Nonaccrual Loans		28,124
Current Accruing Loans		8,722,913
Financing Receivable, before Allowance for Credit Loss, Total		8,778,629
Non-PCI Loans | Consumer lending | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		20,517
Total Nonaccrual Loans		14,865
Current Accruing Loans		6,993,597
Financing Receivable, before Allowance for Credit Loss, Total		7,028,979
Non-PCI Loans | Consumer lending | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		7,064
Total Nonaccrual Loans		10,742
Current Accruing Loans		1,448,930
Financing Receivable, before Allowance for Credit Loss, Total		1,466,736
Non-PCI Loans | Consumer lending | Total residential mortgage
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		27,581
Total Nonaccrual Loans		25,607
Current Accruing Loans		8,442,527
Financing Receivable, before Allowance for Credit Loss, Total		8,495,715
Non-PCI Loans | Consumer lending | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		11
Total Nonaccrual Loans		2,517
Current Accruing Loans		280,386
Financing Receivable, before Allowance for Credit Loss, Total		282,914
Non-PCI Loans | Consumer lending | Accruing Loans 30-59  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		19,722
Non-PCI Loans | Consumer lending | Accruing Loans 30-59  Days Past Due | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		15,443
Non-PCI Loans | Consumer lending | Accruing Loans 30-59  Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		4,273
Non-PCI Loans | Consumer lending | Accruing Loans 30-59  Days Past Due | Total residential mortgage
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		19,716
Non-PCI Loans | Consumer lending | Accruing Loans 30-59  Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		6
Non-PCI Loans | Consumer lending | Accruing Loans 60-89  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		7,870
Non-PCI Loans | Consumer lending | Accruing Loans 60-89  Days Past Due | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		5,074
Non-PCI Loans | Consumer lending | Accruing Loans 60-89  Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		2,791
Non-PCI Loans | Consumer lending | Accruing Loans 60-89  Days Past Due | Total residential mortgage
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		7,865
Non-PCI Loans | Consumer lending | Accruing Loans 60-89  Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans		5
Non-PCI Loans | Consumer lending | Nonaccrual Loans Less Than 90  Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		3,412
Non-PCI Loans | Consumer lending | Nonaccrual Loans Less Than 90  Days Past Due | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		1,964
Non-PCI Loans | Consumer lending | Nonaccrual Loans Less Than 90  Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		1,448
Non-PCI Loans | Consumer lending | Nonaccrual Loans Less Than 90  Days Past Due | Total residential mortgage
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		3,412
Non-PCI Loans | Consumer lending | Nonaccrual Loans Less Than 90  Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		0
Non-PCI Loans | Consumer lending | Nonaccrual Loans 90 or More Days  Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		24,712
Non-PCI Loans | Consumer lending | Nonaccrual Loans 90 or More Days  Past Due | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		12,901
Non-PCI Loans | Consumer lending | Nonaccrual Loans 90 or More Days  Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		9,294
Non-PCI Loans | Consumer lending | Nonaccrual Loans 90 or More Days  Past Due | Total residential mortgage
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		22,195
Non-PCI Loans | Consumer lending | Nonaccrual Loans 90 or More Days  Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Nonaccrual Loans		$ 2,517