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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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Allowance for loan losses
Beginning balance			$ 311,322
Charge-offs	$ (317)	$ (13,300)	(390)	$ (13,400)
Ending balance	330,625	301,550	330,625	301,550
Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Beginning balance			191,340
Ending balance	205,503		205,503
Commercial lending \| Commercial real estate (“CRE”)
Allowance for loan losses
Beginning balance			39,053
Ending balance	40,517		40,517
Commercial lending \| Real estate loan \| Multifamily residential
Allowance for loan losses
Beginning balance			19,283
Ending balance	18,574		18,574
Commercial lending \| Construction and land
Allowance for loan losses
Beginning balance			20,282
Ending balance	22,961		22,961
Consumer lending \| Real estate loan \| Single-family residential
Allowance for loan losses
Beginning balance			31,340
Ending balance	32,763		32,763
Consumer lending \| HELOCs
Allowance for loan losses
Beginning balance			5,774
Ending balance	6,177		6,177
Consumer lending \| Other consumer
Allowance for loan losses
Beginning balance			4,250
Ending balance	4,130		4,130
Non-PCI Loans
Allowance for loan losses
Beginning balance	317,880	297,607	311,300	287,070
(Reversal of) provision for loan losses	20,740	15,139	41,388	35,072
Charge-offs	(11,759)	(13,696)	(29,017)	(32,159)
Recoveries	4,121	3,101	6,942	11,760
Net charge-offs	(7,638)	(10,595)	(22,075)	(20,399)
Foreign currency translation adjustments	(362)	(640)	7	(232)
Ending balance	330,620	301,511	330,620	301,511
Non-PCI Loans \| Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Charge-offs	(11,745)	(13,534)	(28,989)	(31,979)
Recoveries	1,713	1,151	3,964	8,430
Non-PCI Loans \| Commercial lending \| Commercial real estate (“CRE”)
Allowance for loan losses
Recoveries	1,837	2	2,059	429
Non-PCI Loans \| Commercial lending \| Real estate loan \| Multifamily residential
Allowance for loan losses
Recoveries	53	1,061	334	1,394
Non-PCI Loans \| Commercial lending \| Construction and land
Allowance for loan losses
Recoveries	439	258	502	693
Non-PCI Loans \| Consumer lending \| Real estate loan \| Single-family residential
Allowance for loan losses
Charge-offs	0	0	0	(1)
Recoveries	72	629	74	813
Non-PCI Loans \| Consumer lending \| HELOCs
Allowance for loan losses
Recoveries	0	0	2	0
Non-PCI Loans \| Consumer lending \| Other consumer
Allowance for loan losses
Charge-offs	(14)	(162)	(28)	(179)
Recoveries	7	0	7	1
PCI Loans
Allowance for loan losses
Beginning balance	14	47	22	58
(Reversal of) provision for loan losses	(9)	(8)	(17)	(19)
Ending balance	5	$ 39	5	$ 39
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			22
Ending balance	5		5
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