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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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Allowance for loan losses
Beginning balance			$ 311,322
Charge-offs	$ (36)	$ (110)	(426)	$ (13,500)
Ending balance	345,576	310,041	345,576	310,041
Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Beginning balance			189,117
Ending balance	218,869		218,869
Commercial lending \| Commercial real estate (“CRE”)
Allowance for loan losses
Beginning balance			40,666
Ending balance	37,473		37,473
Commercial lending \| Real estate loan \| Multifamily residential
Allowance for loan losses
Beginning balance			19,885
Ending balance	20,307		20,307
Commercial lending \| Construction and land
Allowance for loan losses
Beginning balance			20,290
Ending balance	29,171		29,171
Consumer lending \| Real estate loan \| Single-family residential
Allowance for loan losses
Beginning balance			31,340
Ending balance	29,935		29,935
Consumer lending \| HELOCs
Allowance for loan losses
Beginning balance			5,774
Ending balance	5,856		5,856
Consumer lending \| Other consumer
Allowance for loan losses
Beginning balance			4,250
Ending balance	3,965		3,965
Non-PCI Loans
Allowance for loan losses
Beginning balance	330,620	301,511	311,300	287,070
(Reversal of) provision for loan losses	37,884	12,650	79,272	47,722
Charge-offs	(26,142)	(4,468)	(55,159)	(36,627)
Recoveries	3,679	809	10,621	12,569
Net charge-offs	(22,463)	(3,659)	(44,538)	(24,058)
Foreign currency translation adjustments	(465)	(492)	(458)	(724)
Ending balance	345,576	310,010	345,576	310,010
Non-PCI Loans \| Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Charge-offs	(25,098)	(4,462)	(54,087)	(36,441)
Recoveries	1,648	411	5,612	8,841
Non-PCI Loans \| Commercial lending \| Commercial real estate (“CRE”)
Allowance for loan losses
Charge-offs	(1,021)	0	(1,021)	0
Recoveries	1,896	2	3,955	431
Non-PCI Loans \| Commercial lending \| Real estate loan \| Multifamily residential
Allowance for loan losses
Recoveries	42	77	376	1,471
Non-PCI Loans \| Commercial lending \| Construction and land
Allowance for loan losses
Recoveries	21	23	523	716
Non-PCI Loans \| Consumer lending \| Real estate loan \| Single-family residential
Allowance for loan losses
Charge-offs	(11)	0	(11)	(1)
Recoveries	60	295	134	1,108
Non-PCI Loans \| Consumer lending \| HELOCs
Allowance for loan losses
Recoveries	5	0	7	0
Non-PCI Loans \| Consumer lending \| Other consumer
Allowance for loan losses
Charge-offs	(12)	(6)	(40)	(185)
Recoveries	7	1	14	2
PCI Loans
Allowance for loan losses
Beginning balance	5	39	22	58
(Reversal of) provision for loan losses	(5)	(8)	(22)	(27)
Ending balance	0	$ 31	0	$ 31
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	0		0
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