Loans Receivable and Allowance for Credit Losses (Aging Analysis on Non-PCI Loans) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Nonaccrual and Past Due Loans
Number of days beyond loan classified nonaccrual	90 days
Total loans	$ 33,730,377	$ 32,385,189
Commercial lending
Nonaccrual and Past Due Loans
Total loans	25,318,543	24,326,631
Commercial lending | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total loans	12,402,967	12,056,970
Commercial lending | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total loans	9,868,433	9,449,835
Commercial lending | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total loans	2,372,345	2,281,032
Commercial lending | Construction and land
Nonaccrual and Past Due Loans
Total loans	674,798	538,794
Consumer lending
Nonaccrual and Past Due Loans
Total loans	8,411,834	8,058,558
Consumer lending | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total loans	6,494,882	6,036,454
Consumer lending | HELOCs
Nonaccrual and Past Due Loans
Total loans	1,575,150	1,690,834
Consumer lending | Other consumer
Nonaccrual and Past Due Loans
Total loans	341,802	331,270
Non-PCI Loans
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	61,160	79,230
Total Nonaccrual Loans	118,014	85,693
Current Accruing Loans	33,280,336	31,912,243
Total loans	33,459,510	32,077,166
Non-PCI Loans | Accruing Loans 30-59 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	47,535	50,382
Non-PCI Loans | Accruing Loans 60-89 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	13,625	28,848
Non-PCI Loans | Nonaccrual Loans Less Than 90 Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	41,028	23,800
Non-PCI Loans | Nonaccrual Loans 90 or More Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	76,986	61,893
Non-PCI Loans | Commercial lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	29,609	52,323
Total Nonaccrual Loans	95,091	69,318
Current Accruing Loans	25,021,480	24,003,018
Total loans	25,146,180	24,124,659
Non-PCI Loans | Commercial lending | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	18,054	40,202
Total Nonaccrual Loans	73,150	43,840
Current Accruing Loans	12,309,886	11,970,776
Total loans	12,401,090	12,054,818
Non-PCI Loans | Commercial lending | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	11,169	7,740
Total Nonaccrual Loans	20,914	24,218
Current Accruing Loans	9,690,499	9,252,625
Total loans	9,722,582	9,284,583
Non-PCI Loans | Commercial lending | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	386	4,174
Total Nonaccrual Loans	1,027	1,260
Current Accruing Loans	2,346,338	2,241,072
Total loans	2,347,751	2,246,506
Non-PCI Loans | Commercial lending | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	207
Total Nonaccrual Loans	0	0
Current Accruing Loans	674,757	538,545
Total loans	674,757	538,752
Non-PCI Loans | Commercial lending | Accruing Loans 30-59 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	23,363	33,153
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	11,878	21,032
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	11,099	7,740
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	386	4,174
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	207
Non-PCI Loans | Commercial lending | Accruing Loans 60-89 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	6,246	19,170
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	6,176	19,170
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	70	0
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	0	0
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	0
Non-PCI Loans | Commercial lending | Nonaccrual Loans Less Than 90 Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	40,259	21,868
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	36,208	17,097
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	3,038	3,704
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	1,013	1,067
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	0
Non-PCI Loans | Commercial lending | Nonaccrual Loans 90 or More Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	54,832	47,450
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	36,942	26,743
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	17,876	20,514
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	14	193
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	0
Non-PCI Loans | Consumer lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	31,551	26,907
Total Nonaccrual Loans	22,923	16,375
Current Accruing Loans	8,258,856	7,909,225
Total loans	8,313,330	7,952,507
Non-PCI Loans | Consumer lending | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	20,449	22,495
Total Nonaccrual Loans	13,075	5,259
Current Accruing Loans	6,370,104	5,911,504
Total loans	6,403,628	5,939,258
Non-PCI Loans | Consumer lending | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	11,084	4,389
Total Nonaccrual Loans	7,344	8,614
Current Accruing Loans	1,549,472	1,668,976
Total loans	1,567,900	1,681,979
Non-PCI Loans | Consumer lending | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	18	23
Total Nonaccrual Loans	2,504	2,502
Current Accruing Loans	339,280	328,745
Total loans	341,802	331,270
Non-PCI Loans | Consumer lending | Accruing Loans 30-59 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	24,172	17,229
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	18,052	14,645
Non-PCI Loans | Consumer lending | Accruing Loans 30-59 Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	6,116	2,573
Non-PCI Loans | Consumer lending | Accruing Loans 30-59 Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	4	11
Non-PCI Loans | Consumer lending | Accruing Loans 60-89 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	7,379	9,678
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	2,397	7,850
Non-PCI Loans | Consumer lending | Accruing Loans 60-89 Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	4,968	1,816
Non-PCI Loans | Consumer lending | Accruing Loans 60-89 Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	14	12
Non-PCI Loans | Consumer lending | Nonaccrual Loans Less Than 90 Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	769	1,932
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	712	509
Non-PCI Loans | Consumer lending | Nonaccrual Loans Less Than 90 Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	57	1,423
Non-PCI Loans | Consumer lending | Nonaccrual Loans Less Than 90 Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	0	0
Non-PCI Loans | Consumer lending | Nonaccrual Loans 90 or More Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	22,154	14,443
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	12,363	4,750
Non-PCI Loans | Consumer lending | Nonaccrual Loans 90 or More Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	7,287	7,191
Non-PCI Loans | Consumer lending | Nonaccrual Loans 90 or More Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	$ 2,504	$ 2,502