Loans Receivable and Allowance for Credit Losses (Details 3) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	$ 28,525,357	$ 25,503,139
CRE
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	9,527,180	8,690,863
CRE | Income producing
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	8,843,776	8,016,109
CRE | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	572,027	551,560
CRE | Land
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	111,377	123,194
C&I
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	10,645,156	9,640,563
C&I | Commercial business
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	9,776,254	8,959,633
C&I | Trade finance
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	868,902	680,930
Residential
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	6,232,965	5,095,718
Residential | Real estate loan | Single-family
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	4,356,009	3,509,779
Residential | Real estate loan | Multifamily
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	1,876,956	1,585,939
Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	2,120,056	2,075,995
Non-PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	27,993,084	24,860,694
Non-PCI Loans | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	27,325,373	24,177,983
Non-PCI Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	278,550	212,927
Non-PCI Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	368,142	464,609
Non-PCI Loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	21,019	5,167
Non-PCI Loans | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	8
Non-PCI Loans | CRE
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	9,213,552	8,340,497
Non-PCI Loans | CRE | Income producing
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	8,530,519	7,667,661
Non-PCI Loans | CRE | Income producing | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	8,341,970	7,476,804
Non-PCI Loans | CRE | Income producing | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	74,028	29,005
Non-PCI Loans | CRE | Income producing | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	114,521	161,852
Non-PCI Loans | CRE | Income producing | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
Non-PCI Loans | CRE | Income producing | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
Non-PCI Loans | CRE | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	572,027	551,560
Non-PCI Loans | CRE | Construction | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	540,851	551,560
Non-PCI Loans | CRE | Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	22,176	0
Non-PCI Loans | CRE | Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	9,000	0
Non-PCI Loans | CRE | Construction | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
Non-PCI Loans | CRE | Construction | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
Non-PCI Loans | CRE | Land
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	111,006	121,276
Non-PCI Loans | CRE | Land | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	96,160	107,976
Non-PCI Loans | CRE | Land | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
Non-PCI Loans | CRE | Land | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	14,846	13,290
Non-PCI Loans | CRE | Land | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	10
Non-PCI Loans | CRE | Land | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
Non-PCI Loans | C&I
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	10,632,590	9,602,176
Non-PCI Loans | C&I | Commercial business
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	9,763,688	8,921,246
Non-PCI Loans | C&I | Commercial business | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	9,447,163	8,559,674
Non-PCI Loans | C&I | Commercial business | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	142,531	155,276
Non-PCI Loans | C&I | Commercial business | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	152,975	201,139
Non-PCI Loans | C&I | Commercial business | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	21,019	5,157
Non-PCI Loans | C&I | Commercial business | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
Non-PCI Loans | C&I | Trade finance
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	868,902	680,930
Non-PCI Loans | C&I | Trade finance | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	830,268	635,027
Non-PCI Loans | C&I | Trade finance | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	18,631	9,435
Non-PCI Loans | C&I | Trade finance | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	20,003	36,460
Non-PCI Loans | C&I | Trade finance | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
Non-PCI Loans | C&I | Trade finance | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	8
Non-PCI Loans | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	6,042,328	4,860,954
Non-PCI Loans | Residential | Real estate loan | Single-family
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	4,234,017	3,370,669
Non-PCI Loans | Residential | Real estate loan | Single-family | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	4,199,554	3,341,015
Non-PCI Loans | Residential | Real estate loan | Single-family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	11,501	10,179
Non-PCI Loans | Residential | Real estate loan | Single-family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	22,962	19,475
Non-PCI Loans | Residential | Real estate loan | Single-family | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
Non-PCI Loans | Residential | Real estate loan | Single-family | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
Non-PCI Loans | Residential | Real estate loan | Multifamily
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	1,808,311	1,490,285
Non-PCI Loans | Residential | Real estate loan | Multifamily | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	1,789,351	1,462,522
Non-PCI Loans | Residential | Real estate loan | Multifamily | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	2,268
Non-PCI Loans | Residential | Real estate loan | Multifamily | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	18,960	25,495
Non-PCI Loans | Residential | Real estate loan | Multifamily | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
Non-PCI Loans | Residential | Real estate loan | Multifamily | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
Non-PCI Loans | Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	2,104,614	2,057,067
Non-PCI Loans | Consumer | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	2,080,056	2,043,405
Non-PCI Loans | Consumer | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	9,683	6,764
Non-PCI Loans | Consumer | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	14,875	6,898
Non-PCI Loans | Consumer | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
Non-PCI Loans | Consumer | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	532,273	642,445
PCI Loans | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	469,854	568,844
PCI Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	2,223	5,566
PCI Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	60,196	68,035
PCI Loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | CRE
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	313,628	350,366
PCI Loans | CRE | Income producing
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	313,257	348,448
PCI Loans | CRE | Income producing | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	261,907	293,529
PCI Loans | CRE | Income producing | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	3,239
PCI Loans | CRE | Income producing | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	51,350	51,680
PCI Loans | CRE | Income producing | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | CRE | Income producing | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | CRE | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | CRE | Land
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	371	1,918
PCI Loans | CRE | Land | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	44	1,562
PCI Loans | CRE | Land | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | CRE | Land | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	327	356
PCI Loans | CRE | Land | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | CRE | Land | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | C&I
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	12,566	38,387
PCI Loans | C&I | Commercial business
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	12,566	38,387
PCI Loans | C&I | Commercial business | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	11,205	33,885
PCI Loans | C&I | Commercial business | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	90	772
PCI Loans | C&I | Commercial business | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	1,271	3,730
PCI Loans | C&I | Commercial business | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | C&I | Commercial business | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | C&I | Trade finance
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	190,637	234,764
PCI Loans | Residential | Real estate loan | Single-family
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	121,992	139,110
PCI Loans | Residential | Real estate loan | Single-family | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	118,281	136,245
PCI Loans | Residential | Real estate loan | Single-family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	1,769	1,239
PCI Loans | Residential | Real estate loan | Single-family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	1,942	1,626
PCI Loans | Residential | Real estate loan | Single-family | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | Residential | Real estate loan | Single-family | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | Residential | Real estate loan | Multifamily
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	68,645	95,654
PCI Loans | Residential | Real estate loan | Multifamily | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	64,455	86,190
PCI Loans | Residential | Real estate loan | Multifamily | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | Residential | Real estate loan | Multifamily | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	4,190	9,464
PCI Loans | Residential | Real estate loan | Multifamily | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | Residential | Real estate loan | Multifamily | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	15,442	18,928
PCI Loans | Consumer | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	13,962	17,433
PCI Loans | Consumer | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	364	316
PCI Loans | Consumer | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	1,116	1,179
PCI Loans | Consumer | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	0	0
PCI Loans | Consumer | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-investment	$ 0	$ 0