Loans Receivable and Allowance for Credit Losses (Aging Analysis on Non-PCI Loans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Nonaccrual and Past Due Loans
Number of days beyond loan classified nonaccrual	90 days
Total loans	$ 32,385,189	$ 28,975,718
Commercial Lending
Nonaccrual and Past Due Loans
Total loans	24,326,631	22,210,001
Commercial Lending | C&I
Nonaccrual and Past Due Loans
Total loans	12,056,970	10,697,231
Commercial Lending | CRE
Nonaccrual and Past Due Loans
Total loans	9,449,835	8,936,897
Commercial Lending | Residential loan | Multifamily
Nonaccrual and Past Due Loans
Total loans	2,281,032	1,916,176
Commercial Lending | Construction and land
Nonaccrual and Past Due Loans
Total loans	538,794	659,697
Consumer Lending
Nonaccrual and Past Due Loans
Total loans	8,058,558	6,765,717
Consumer Lending | Residential loan | Single-family
Nonaccrual and Past Due Loans
Total loans	6,036,454	4,646,289
Consumer Lending | HELOCs
Nonaccrual and Past Due Loans
Total loans	1,690,834	1,782,924
Consumer Lending | Other consumer
Nonaccrual and Past Due Loans
Total loans	331,270	336,504
Non-PCI loans
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	79,230	67,677
Total Nonaccrual Loans	85,693	114,309
Current Accruing Loans	31,912,243	28,311,445
Total loans	32,077,166	28,493,431
Non-PCI loans | Commercial Lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	52,323	40,544
Total Nonaccrual Loans	69,318	101,889
Current Accruing Loans	24,003,018	21,716,666
Total loans	24,124,659	21,859,099
Non-PCI loans | Commercial Lending | C&I
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	40,202	31,046
Total Nonaccrual Loans	43,840	69,213
Current Accruing Loans	11,970,776	10,585,177
Total loans	12,054,818	10,685,436
Non-PCI loans | Commercial Lending | CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	7,740	3,880
Total Nonaccrual Loans	24,218	26,986
Current Accruing Loans	9,252,625	8,628,343
Total loans	9,284,583	8,659,209
Non-PCI loans | Commercial Lending | Residential loan | Multifamily
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	4,174	4,860
Total Nonaccrual Loans	1,260	1,717
Current Accruing Loans	2,241,072	1,848,551
Total loans	2,246,506	1,855,128
Non-PCI loans | Commercial Lending | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	207	758
Total Nonaccrual Loans	0	3,973
Current Accruing Loans	538,545	654,595
Total loans	538,752	659,326
Non-PCI loans | Consumer Lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	26,907	27,133
Total Nonaccrual Loans	16,375	12,420
Current Accruing Loans	7,909,225	6,594,779
Total loans	7,952,507	6,634,332
Non-PCI loans | Consumer Lending | Residential loan | Single-family
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	22,495	18,624
Total Nonaccrual Loans	5,259	5,923
Current Accruing Loans	5,911,504	4,504,364
Total loans	5,939,258	4,528,911
Non-PCI loans | Consumer Lending | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	4,389	8,472
Total Nonaccrual Loans	8,614	4,006
Current Accruing Loans	1,668,976	1,756,439
Total loans	1,681,979	1,768,917
Non-PCI loans | Consumer Lending | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	23	37
Total Nonaccrual Loans	2,502	2,491
Current Accruing Loans	328,745	333,976
Total loans	331,270	336,504
Non-PCI loans | Accruing Loans 30-59 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	50,382	57,551
Non-PCI loans | Accruing Loans 30-59 Days Past Due | Commercial Lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	33,153	39,982
Non-PCI loans | Accruing Loans 30-59 Days Past Due | Commercial Lending | C&I
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	21,032	30,964
Non-PCI loans | Accruing Loans 30-59 Days Past Due | Commercial Lending | CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	7,740	3,414
Non-PCI loans | Accruing Loans 30-59 Days Past Due | Commercial Lending | Residential loan | Multifamily
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	4,174	4,846
Non-PCI loans | Accruing Loans 30-59 Days Past Due | Commercial Lending | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	207	758
Non-PCI loans | Accruing Loans 30-59 Days Past Due | Consumer Lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	17,229	17,569
Non-PCI loans | Accruing Loans 30-59 Days Past Due | Consumer Lending | Residential loan | Single-family
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	14,645	13,269
Non-PCI loans | Accruing Loans 30-59 Days Past Due | Consumer Lending | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	2,573	4,286
Non-PCI loans | Accruing Loans 30-59 Days Past Due | Consumer Lending | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	11	14
Non-PCI loans | Accruing Loans 60-89 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	28,848	10,126
Non-PCI loans | Accruing Loans 60-89 Days Past Due | Commercial Lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	19,170	562
Non-PCI loans | Accruing Loans 60-89 Days Past Due | Commercial Lending | C&I
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	19,170	82
Non-PCI loans | Accruing Loans 60-89 Days Past Due | Commercial Lending | CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	466
Non-PCI loans | Accruing Loans 60-89 Days Past Due | Commercial Lending | Residential loan | Multifamily
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	14
Non-PCI loans | Accruing Loans 60-89 Days Past Due | Commercial Lending | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	0
Non-PCI loans | Accruing Loans 60-89 Days Past Due | Consumer Lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	9,678	9,564
Non-PCI loans | Accruing Loans 60-89 Days Past Due | Consumer Lending | Residential loan | Single-family
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	7,850	5,355
Non-PCI loans | Accruing Loans 60-89 Days Past Due | Consumer Lending | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	1,816	4,186
Non-PCI loans | Accruing Loans 60-89 Days Past Due | Consumer Lending | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	12	23
Non-PCI loans | Nonaccrual Loans Less Than 90 Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	23,800	34,351
Non-PCI loans | Nonaccrual Loans Less Than 90 Days Past Due | Commercial Lending
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	21,868	34,256
Non-PCI loans | Nonaccrual Loans Less Than 90 Days Past Due | Commercial Lending | C&I
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	17,097	27,408
Non-PCI loans | Nonaccrual Loans Less Than 90 Days Past Due | Commercial Lending | CRE
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	3,704	5,430
Non-PCI loans | Nonaccrual Loans Less Than 90 Days Past Due | Commercial Lending | Residential loan | Multifamily
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	1,067	1,418
Non-PCI loans | Nonaccrual Loans Less Than 90 Days Past Due | Commercial Lending | Construction and land
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	0	0
Non-PCI loans | Nonaccrual Loans Less Than 90 Days Past Due | Consumer Lending
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	1,932	95
Non-PCI loans | Nonaccrual Loans Less Than 90 Days Past Due | Consumer Lending | Residential loan | Single-family
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	509	6
Non-PCI loans | Nonaccrual Loans Less Than 90 Days Past Due | Consumer Lending | HELOCs
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	1,423	89
Non-PCI loans | Nonaccrual Loans Less Than 90 Days Past Due | Consumer Lending | Other consumer
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	0	0
Non-PCI loans | Nonaccrual Loans 90 or More Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	61,893	79,958
Non-PCI loans | Nonaccrual Loans 90 or More Days Past Due | Commercial Lending
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	47,450	67,633
Non-PCI loans | Nonaccrual Loans 90 or More Days Past Due | Commercial Lending | C&I
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	26,743	41,805
Non-PCI loans | Nonaccrual Loans 90 or More Days Past Due | Commercial Lending | CRE
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	20,514	21,556
Non-PCI loans | Nonaccrual Loans 90 or More Days Past Due | Commercial Lending | Residential loan | Multifamily
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	193	299
Non-PCI loans | Nonaccrual Loans 90 or More Days Past Due | Commercial Lending | Construction and land
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	0	3,973
Non-PCI loans | Nonaccrual Loans 90 or More Days Past Due | Consumer Lending
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	14,443	12,325
Non-PCI loans | Nonaccrual Loans 90 or More Days Past Due | Consumer Lending | Residential loan | Single-family
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	4,750	5,917
Non-PCI loans | Nonaccrual Loans 90 or More Days Past Due | Consumer Lending | HELOCs
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	7,191	3,917
Non-PCI loans | Nonaccrual Loans 90 or More Days Past Due | Consumer Lending | Other consumer
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	$ 2,502	$ 2,491