Loans Receivable and Allowance for Credit Losses (Aging Analysis on Non-PCI Loans) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Nonaccrual and Past Due Loans
Total loans	$ 34,024,976	$ 32,385,189
Commercial lending
Nonaccrual and Past Due Loans
Total loans	25,359,688	24,326,631
Commercial lending | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total loans	12,301,002	12,056,970
Commercial lending | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total loans	9,749,583	9,260,199
Commercial lending | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total loans	2,589,203	2,470,668
Commercial lending | Construction and land
Nonaccrual and Past Due Loans
Total loans	719,900	538,794
Consumer lending
Nonaccrual and Past Due Loans
Total loans	8,665,288	8,058,558
Consumer lending | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total loans	6,811,014	6,036,454
Consumer lending | HELOCs
Nonaccrual and Past Due Loans
Total loans	1,540,121	1,690,834
Consumer lending | Other consumer
Nonaccrual and Past Due Loans
Total loans	314,153	331,270
Non-PCI Loans
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	69,773	79,230
Total Nonaccrual Loans	132,226	85,693
Current Accruing Loans	33,582,271	31,912,243
Total loans	33,784,270	32,077,166
Non-PCI Loans | Accruing Loans 30-59 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	49,233	50,382
Non-PCI Loans | Accruing Loans 60-89 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	20,540	28,848
Non-PCI Loans | Nonaccrual Loans Less Than 90 Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	41,796	23,800
Non-PCI Loans | Nonaccrual Loans 90 or More Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	90,430	61,893
Non-PCI Loans | Commercial lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	34,487	52,323
Total Nonaccrual Loans	110,323	69,318
Current Accruing Loans	25,066,300	24,003,018
Total loans	25,211,110	24,124,659
Non-PCI Loans | Commercial lending | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	10,994	40,202
Total Nonaccrual Loans	90,830	43,840
Current Accruing Loans	12,197,339	11,970,776
Total loans	12,299,163	12,054,818
Non-PCI Loans | Commercial lending | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	2,828	7,740
Total Nonaccrual Loans	18,942	24,218
Current Accruing Loans	9,605,560	9,065,207
Total loans	9,627,330	9,097,165
Non-PCI Loans | Commercial lending | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	978	4,174
Total Nonaccrual Loans	551	1,260
Current Accruing Loans	2,563,229	2,428,490
Total loans	2,564,758	2,433,924
Non-PCI Loans | Commercial lending | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	19,687	207
Total Nonaccrual Loans	0	0
Current Accruing Loans	700,172	538,545
Total loans	719,859	538,752
Non-PCI Loans | Commercial lending | Accruing Loans 30-59 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	27,309	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	4,105	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	2,828	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	689	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	19,687	207
Non-PCI Loans | Commercial lending | Accruing Loans 60-89 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	7,178	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	6,889	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	0	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	289	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	40,479	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	38,049	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	1,879	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	551	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	69,844	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	52,781	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	17,063	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	0	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	35,286	26,907
Total Nonaccrual Loans	21,903	16,375
Current Accruing Loans	8,515,971	7,909,225
Total loans	8,573,160	7,952,507
Non-PCI Loans | Consumer lending | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	21,877	22,495
Total Nonaccrual Loans	9,484	5,259
Current Accruing Loans	6,694,213	5,911,504
Total loans	6,725,574	5,939,258
Non-PCI Loans | Consumer lending | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	13,339	4,389
Total Nonaccrual Loans	9,924	8,614
Current Accruing Loans	1,510,170	1,668,976
Total loans	1,533,433	1,681,979
Non-PCI Loans | Consumer lending | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	70	23
Total Nonaccrual Loans	2,495	2,502
Current Accruing Loans	311,588	328,745
Total loans	314,153	331,270
Non-PCI Loans | Consumer lending | Accruing Loans 30-59 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	21,924	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	13,503	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	8,372	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	49	11
Non-PCI Loans | Consumer lending | Accruing Loans 60-89 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	13,362	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	8,374	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	4,967	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	21	12
Non-PCI Loans | Consumer lending | Nonaccrual Loans Less Than 90 Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	1,317	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	1,122	509
Non-PCI Loans | Consumer lending | Nonaccrual Loans Less Than 90 Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	195	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	20,586	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	8,362	4,750
Non-PCI Loans | Consumer lending | Nonaccrual Loans 90 or More Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	9,729	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	$ 2,495	$ 2,502