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Loans Receivable and Allowance for Credit Losses (Summary of Activities in Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Allowance for loan losses
Beginning balance			$ 287,128
Charge-offs	$ (110)	$ (232)	(13,500)	$ (441)
Ending balance	310,041	285,926	310,041	285,926
Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Beginning balance			163,058
Ending balance	181,757		181,757
Commercial lending \| Commercial real estate (“CRE”)
Allowance for loan losses
Beginning balance			41,237
Ending balance	45,428		45,428
Commercial lending \| Real estate loan \| Multifamily residential
Allowance for loan losses
Beginning balance			19,109
Ending balance	17,755		17,755
Commercial lending \| Construction and land
Allowance for loan losses
Beginning balance			26,881
Ending balance	24,433		24,433
Consumer lending \| Real estate loan \| Single-family residential
Allowance for loan losses
Beginning balance			26,362
Ending balance	30,645		30,645
Consumer lending \| HELOCs
Allowance for loan losses
Beginning balance			7,354
Ending balance	5,762		5,762
Consumer lending \| Other consumer
Allowance for loan losses
Beginning balance			3,127
Ending balance	4,261		4,261
Non-PCI Loans
Allowance for loan losses
Beginning balance	301,511	276,238	287,070	260,402
(Reversal of) provision for loan losses	12,650	13,458	47,722	32,184
Charge-offs	(4,468)	(7,424)	(36,627)	(20,024)
Recoveries	809	3,383	12,569	12,843
Net charge-offs	(3,659)	(4,041)	(24,058)	(7,181)
Foreign currency translation adjustments	(492)	203	(724)	453
Ending balance	310,010	285,858	310,010	285,858
Non-PCI Loans \| Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Charge-offs	(4,462)	(7,359)	(36,441)	(19,802)
Recoveries	411	1,962	8,841	9,205
Non-PCI Loans \| Commercial lending \| Commercial real estate (“CRE”)
Allowance for loan losses
Recoveries	2	549	431	1,541
Non-PCI Loans \| Commercial lending \| Real estate loan \| Multifamily residential
Allowance for loan losses
Recoveries	77	634	1,471	1,329
Non-PCI Loans \| Commercial lending \| Construction and land
Allowance for loan losses
Charge-offs	0	0	0	(149)
Recoveries	23	61	716	173
Non-PCI Loans \| Consumer lending \| Real estate loan \| Single-family residential
Allowance for loan losses
Charge-offs	0	0	(1)	(1)
Recoveries	295	175	1,108	429
Non-PCI Loans \| Consumer lending \| HELOCs
Allowance for loan losses
Charge-offs	0	(55)	0	(55)
Recoveries	0	0	0	24
Non-PCI Loans \| Consumer lending \| Other consumer
Allowance for loan losses
Charge-offs	(6)	(10)	(185)	(17)
Recoveries	1	2	2	142
PCI Loans
Allowance for loan losses
Beginning balance	39	78	58	118
(Reversal of) provision for loan losses	(8)	(10)	(27)	(50)
Ending balance	31	$ 68	31	$ 68
PCI Loans \| Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Beginning balance			0
Ending balance	0		0
PCI Loans \| Commercial lending \| Commercial real estate (“CRE”)
Allowance for loan losses
Beginning balance			58
Ending balance	31		31
PCI Loans \| Commercial lending \| Real estate loan \| Multifamily residential
Allowance for loan losses
Beginning balance			0
Ending balance	0		0
PCI Loans \| Commercial lending \| Construction and land
Allowance for loan losses
Beginning balance			0
Ending balance	0		0
PCI Loans \| Consumer lending \| Real estate loan \| Single-family residential
Allowance for loan losses
Beginning balance			0
Ending balance	0		0
PCI Loans \| Consumer lending \| HELOCs
Allowance for loan losses
Beginning balance			0
Ending balance	0		0
PCI Loans \| Consumer lending \| Other consumer
Allowance for loan losses
Beginning balance			0
Ending balance	$ 0		$ 0