Loans Receivable and Allowance for Credit Losses (Summary of Activities in Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for loan losses
Allowance, beginning of period	$ 287,128	$ 260,520
Gross charge-offs	(14,600)	(473)	$ (1,900)
Allowance, end of period	311,322	287,128	260,520
Commercial Lending \| C&I
Allowance for loan losses
Allowance, beginning of period	163,058
Allowance, end of period	191,340	163,058
Commercial Lending \| CRE
Allowance for loan losses
Allowance, beginning of period	41,237
Allowance, end of period	39,053	41,237
Commercial Lending \| Residential loan \| Multifamily
Allowance for loan losses
Allowance, beginning of period	19,109
Allowance, end of period	19,283	19,109
Commercial Lending \| Construction and land
Allowance for loan losses
Allowance, beginning of period	26,881
Allowance, end of period	20,282	26,881
Consumer Lending \| Residential loan \| Single-family
Allowance for loan losses
Allowance, beginning of period	26,362
Allowance, end of period	31,340	26,362
Consumer Lending \| HELOCs
Allowance for loan losses
Allowance, beginning of period	7,354
Allowance, end of period	5,774	7,354
Consumer Lending \| Other consumer
Allowance for loan losses
Allowance, beginning of period	3,127
Allowance, end of period	4,250	3,127
Non-PCI loans
Allowance for loan losses
Allowance, beginning of period	287,070	260,402	264,600
Provision for (reversal of) on loans	65,043	49,129	31,959
Gross charge-offs	(59,433)	(38,975)	(48,508)
Gross recoveries	19,363	15,820	12,901
Net charge-offs	(40,070)	(23,155)	(35,607)
Foreign currency translation adjustments	(743)	694	(550)
Allowance, end of period	311,300	287,070	260,402
Non-PCI loans \| Commercial Lending \| C&I
Allowance for loan losses
Gross charge-offs	(59,244)	(38,118)	(47,739)
Gross recoveries	10,417	11,371	9,003
Non-PCI loans \| Commercial Lending \| CRE
Allowance for loan losses
Gross charge-offs	0	0	(464)
Gross recoveries	5,194	2,111	1,488
Non-PCI loans \| Commercial Lending \| Residential loan \| Multifamily
Allowance for loan losses
Gross charge-offs	0	(635)	(29)
Gross recoveries	1,757	1,357	1,476
Non-PCI loans \| Commercial Lending \| Construction and land
Allowance for loan losses
Gross charge-offs	0	(149)	(117)
Gross recoveries	740	259	203
Non-PCI loans \| Consumer Lending \| Residential loan \| Single-family
Allowance for loan losses
Gross charge-offs	(1)	(1)	(137)
Gross recoveries	1,214	546	401
Non-PCI loans \| Consumer Lending \| HELOCs
Allowance for loan losses
Gross charge-offs	0	(55)	(9)
Gross recoveries	38	24	7
Non-PCI loans \| Consumer Lending \| Other consumer
Allowance for loan losses
Gross charge-offs	(188)	(17)	(13)
Gross recoveries	3	152	323
PCI Loans
Allowance for loan losses
Allowance, beginning of period	58	118	359
Provision for (reversal of) on loans	(36)	(60)	(241)
Allowance, end of period	22	58	$ 118
PCI Loans \| Commercial Lending \| C&I
Allowance for loan losses
Allowance, beginning of period	0
Allowance, end of period	0	0
PCI Loans \| Commercial Lending \| CRE
Allowance for loan losses
Allowance, beginning of period	58
Allowance, end of period	22	58
PCI Loans \| Commercial Lending \| Residential loan \| Multifamily
Allowance for loan losses
Allowance, beginning of period	0
Allowance, end of period	0	0
PCI Loans \| Commercial Lending \| Construction and land
Allowance for loan losses
Allowance, beginning of period	0
Allowance, end of period	0	0
PCI Loans \| Consumer Lending \| Residential loan \| Single-family
Allowance for loan losses
Allowance, beginning of period	0
Allowance, end of period	0	0
PCI Loans \| Consumer Lending \| HELOCs
Allowance for loan losses
Allowance, beginning of period	0
Allowance, end of period	0	0
PCI Loans \| Consumer Lending \| Other consumer
Allowance for loan losses
Allowance, beginning of period	0
Allowance, end of period	$ 0	$ 0

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of gain (loss) from converting allowance reserve for credit loss to currency of reporting entity from amount denominated or measured in a different currency, which decreases (increases) the allowance for loan and lease losses.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount, after recoveries, of loans and leases that have been written-off.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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