Loans Receivable and Allowance for Credit Losses (Aging Analysis on Non-PCI Loans) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Nonaccrual and Past Due Loans
Number of days beyond loan classified nonaccrual	90 days
Total loans	$ 29,555,248	$ 28,975,718
Commercial lending
Nonaccrual and Past Due Loans
Total loans	22,465,245	22,210,001
Commercial lending | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total loans	10,818,304	10,697,231
Commercial lending | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total loans	9,022,746	8,936,897
Commercial lending | Real estate loan | Multifamily
Nonaccrual and Past Due Loans
Total loans	1,954,855	1,916,176
Commercial lending | Construction and land
Nonaccrual and Past Due Loans
Total loans	669,340	659,697
Consumer lending
Nonaccrual and Past Due Loans
Total loans	7,090,003	6,765,717
Consumer lending | Real estate loan | Single-family
Nonaccrual and Past Due Loans
Total loans	4,930,580	4,646,289
Consumer lending | Home equity lines of credit (“HELOCs”)
Nonaccrual and Past Due Loans
Total loans	1,775,443	1,782,924
Consumer lending | Other consumer
Nonaccrual and Past Due Loans
Total loans	383,980	336,504
Non-PCI Loans
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	57,319	67,677
Total Nonaccrual Loans	130,217	114,309
Current Accruing Loans	28,915,309	28,311,445
Total loans	29,102,845	28,493,431
Non-PCI Loans | Accruing Loans 30-59 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	41,076	57,551
Non-PCI Loans | Accruing Loans 60-89 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	13,862	10,126
Non-PCI Loans | Accruing Loans 90 or More Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	2,381	0
Total Nonaccrual Loans	85,255	79,958
Non-PCI Loans | Nonaccrual Loans Less Than 90 Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	44,962	34,351
Non-PCI Loans | Commercial lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	34,540	40,544
Total Nonaccrual Loans	113,326	101,889
Current Accruing Loans	21,990,119	21,716,666
Total loans	22,137,985	21,859,099
Non-PCI Loans | Commercial lending | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	20,797	31,046
Total Nonaccrual Loans	80,807	69,213
Current Accruing Loans	10,705,658	10,585,177
Total loans	10,807,262	10,685,436
Non-PCI Loans | Commercial lending | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	8,967	3,880
Total Nonaccrual Loans	26,496	26,986
Current Accruing Loans	8,727,447	8,628,343
Total loans	8,762,910	8,659,209
Non-PCI Loans | Commercial lending | Real estate loan | Multifamily
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	2,972	4,860
Total Nonaccrual Loans	2,050	1,717
Current Accruing Loans	1,893,495	1,848,551
Total loans	1,898,517	1,855,128
Non-PCI Loans | Commercial lending | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	1,804	758
Total Nonaccrual Loans	3,973	3,973
Current Accruing Loans	663,519	654,595
Total loans	669,296	659,326
Non-PCI Loans | Commercial lending | Accruing Loans 30-59 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	28,401	39,982
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	16,767	30,964
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	6,872	3,414
Non-PCI Loans | Commercial lending | Accruing Loans 30-59 Days Past Due | Real estate loan | Multifamily
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	2,958	4,846
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	1,804	758
Non-PCI Loans | Commercial lending | Accruing Loans 60-89 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	3,758	562
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	1,649	82
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	2,095	466
Non-PCI Loans | Commercial lending | Accruing Loans 60-89 Days Past Due | Real estate loan | Multifamily
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	14	14
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 | Accruing Loans 90 or More Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	2,381	0
Total Nonaccrual Loans	68,396	67,633
Non-PCI Loans | Commercial lending | Accruing Loans 90 or More Days Past Due | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	2,381	0
Total Nonaccrual Loans	42,198	41,805
Non-PCI Loans | Commercial lending | Accruing Loans 90 or More Days Past Due | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	0
Total Nonaccrual Loans	21,175	21,556
Non-PCI Loans | Commercial lending | Accruing Loans 90 or More Days Past Due | Real estate loan | Multifamily
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	0
Total Nonaccrual Loans	1,050	299
Non-PCI Loans | Commercial lending | Accruing Loans 90 or More Days Past Due | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	0
Total Nonaccrual Loans	3,973	3,973
Non-PCI Loans | Commercial lending | Nonaccrual Loans Less Than 90 Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	44,930	34,256
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	38,609	27,408
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	5,321	5,430
Non-PCI Loans | Commercial lending | Nonaccrual Loans Less Than 90 Days Past Due | Real estate loan | Multifamily
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	1,000	1,418
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 | Consumer lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	22,779	27,133
Total Nonaccrual Loans	16,891	12,420
Current Accruing Loans	6,925,190	6,594,779
Total loans	6,964,860	6,634,332
Non-PCI Loans | Consumer lending | Real estate loan | Single-family
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	15,963	18,624
Total Nonaccrual Loans	7,465	5,923
Current Accruing Loans	4,794,666	4,504,364
Total loans	4,818,094	4,528,911
Non-PCI Loans | Consumer lending | Home equity lines of credit (“HELOCs”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	6,790	8,472
Total Nonaccrual Loans	6,935	4,006
Current Accruing Loans	1,749,061	1,756,439
Total loans	1,762,786	1,768,917
Non-PCI Loans | Consumer lending | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	26	37
Total Nonaccrual Loans	2,491	2,491
Current Accruing Loans	381,463	333,976
Total loans	383,980	336,504
Non-PCI Loans | Consumer lending | Accruing Loans 30-59 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	12,675	17,569
Non-PCI Loans | Consumer lending | Accruing Loans 30-59 Days Past Due | Real estate loan | Single-family
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	8,230	13,269
Non-PCI Loans | Consumer lending | Accruing Loans 30-59 Days Past Due | Home equity lines of credit (“HELOCs”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	4,421	4,286
Non-PCI Loans | Consumer lending | Accruing Loans 30-59 Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	24	14
Non-PCI Loans | Consumer lending | Accruing Loans 60-89 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	10,104	9,564
Non-PCI Loans | Consumer lending | Accruing Loans 60-89 Days Past Due | Real estate loan | Single-family
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	7,733	5,355
Non-PCI Loans | Consumer lending | Accruing Loans 60-89 Days Past Due | Home equity lines of credit (“HELOCs”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	2,369	4,186
Non-PCI Loans | Consumer lending | Accruing Loans 60-89 Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	2	23
Non-PCI Loans | Consumer lending | Accruing Loans 90 or More Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	0
Total Nonaccrual Loans	16,859	12,325
Non-PCI Loans | Consumer lending | Accruing Loans 90 or More Days Past Due | Real estate loan | Single-family
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	0
Total Nonaccrual Loans	7,459	5,917
Non-PCI Loans | Consumer lending | Accruing Loans 90 or More Days Past Due | Home equity lines of credit (“HELOCs”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	0
Total Nonaccrual Loans	6,909	3,917
Non-PCI Loans | Consumer lending | Accruing Loans 90 or More Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	0
Total Nonaccrual Loans	2,491	2,491
Non-PCI Loans | Consumer lending | Nonaccrual Loans Less Than 90 Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	32	95
Non-PCI Loans | Consumer lending | Nonaccrual Loans Less Than 90 Days Past Due | Real estate loan | Single-family
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	6	6
Non-PCI Loans | Consumer lending | Nonaccrual Loans Less Than 90 Days Past Due | Home equity lines of credit (“HELOCs”)
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	26	89
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