Loans Receivable and Allowance for Credit Losses (Summary of Activities in Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for loan losses
Allowance, beginning of period	$ 311,322	$ 287,128
Gross charge-offs	(789)	(14,600)	$ (473)
Allowance, end of period	358,287	311,322	287,128
Commercial Lending \| C&I
Allowance for loan losses
Allowance, beginning of period	189,117
Allowance, end of period	238,376	189,117
Commercial Lending \| CRE
Allowance for loan losses
Allowance, beginning of period	40,666
Allowance, end of period	40,509	40,666
Commercial Lending \| Residential loan \| Multifamily
Allowance for loan losses
Allowance, beginning of period	19,885
Allowance, end of period	22,826	19,885
Commercial Lending \| Construction and land
Allowance for loan losses
Allowance, beginning of period	20,290
Allowance, end of period	19,404	20,290
Consumer Lending \| Residential loan \| Single-family
Allowance for loan losses
Allowance, beginning of period	31,340
Allowance, end of period	28,527	31,340
Consumer Lending \| HELOCs
Allowance for loan losses
Allowance, beginning of period	5,774
Allowance, end of period	5,265	5,774
Consumer Lending \| Other consumer
Allowance for loan losses
Allowance, beginning of period	4,250
Allowance, end of period	3,380	4,250
Non-PCI loans
Allowance for loan losses
Allowance, beginning of period	311,300	287,070	260,402
Provision for (reversal of) on loans	100,115	65,043	49,129
Gross charge-offs	(75,067)	(59,433)	(38,975)
Gross recoveries	22,264	19,363	15,820
Net charge-offs	(52,803)	(40,070)	(23,155)
Foreign currency translation adjustments	(325)	(743)	694
Allowance, end of period	358,287	311,300	287,070
Non-PCI loans \| Commercial Lending \| C&I
Allowance for loan losses
Gross charge-offs	(73,985)	(59,244)	(38,118)
Gross recoveries	14,501	10,417	11,371
Non-PCI loans \| Commercial Lending \| CRE
Allowance for loan losses
Gross charge-offs	(1,021)	0	0
Gross recoveries	5,209	5,194	2,111
Non-PCI loans \| Commercial Lending \| Residential loan \| Multifamily
Allowance for loan losses
Gross charge-offs	0	0	(635)
Gross recoveries	1,856	1,757	1,357
Non-PCI loans \| Commercial Lending \| Construction and land
Allowance for loan losses
Gross charge-offs	0	0	(149)
Gross recoveries	536	740	259
Non-PCI loans \| Commercial Lending \| Total CRE
Allowance for loan losses
Gross charge-offs	(1,021)	0	(784)
Gross recoveries	7,601	7,691	3,727
Non-PCI loans \| Consumer Lending \| Residential loan \| Single-family
Allowance for loan losses
Gross charge-offs	(11)	(1)	(1)
Gross recoveries	136	1,214	546
Non-PCI loans \| Consumer Lending \| HELOCs
Allowance for loan losses
Gross charge-offs	0	0	(55)
Gross recoveries	7	38	24
Non-PCI loans \| Consumer Lending \| Total residential mortgage
Allowance for loan losses
Gross charge-offs	(11)	(1)	(56)
Gross recoveries	143	1,252	570
Non-PCI loans \| Consumer Lending \| Other consumer
Allowance for loan losses
Gross charge-offs	(50)	(188)	(17)
Gross recoveries	19	3	152
PCI Loans
Allowance for loan losses
Allowance, beginning of period	22	58	118
Provision for (reversal of) on loans	(22)	(36)	(60)
Allowance, end of period	0	22	$ 58
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	22
Allowance, end of period	0	22
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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