Loans Receivable and Allowance for Credit Losses (Summary of Activities in Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Allowance for loan losses
Beginning balance	$ 311,322
Charge-offs	(73)	$ (85)
Ending balance	317,894	297,654
Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Beginning balance	191,340
Ending balance	189,757
Commercial lending \| Commercial real estate (“CRE”)
Allowance for loan losses
Beginning balance	39,053
Ending balance	39,879
Commercial lending \| Real estate loan \| Multifamily residential
Allowance for loan losses
Beginning balance	19,283
Ending balance	18,514
Commercial lending \| Construction and land
Allowance for loan losses
Beginning balance	20,282
Ending balance	22,349
Consumer lending \| Real estate loan \| Single-family residential
Allowance for loan losses
Beginning balance	31,340
Ending balance	35,759
Consumer lending \| HELOCs
Allowance for loan losses
Beginning balance	5,774
Ending balance	7,401
Consumer lending \| Other consumer
Allowance for loan losses
Beginning balance	4,250
Ending balance	4,235
Non-PCI Loans
Allowance for loan losses
Beginning balance	311,300	287,070
(Reversal of) provision for loan losses	20,648	19,933
Charge-offs	(17,258)	(18,463)
Recoveries	2,821	8,659
Net charge-offs	(14,437)	(9,804)
Foreign currency translation adjustments	369	408
Ending balance	317,880	297,607
Non-PCI Loans \| Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Charge-offs	(17,244)	(18,445)
Recoveries	2,251	7,279
Non-PCI Loans \| Commercial lending \| Commercial real estate (“CRE”)
Allowance for loan losses
Recoveries	222	427
Non-PCI Loans \| Commercial lending \| Real estate loan \| Multifamily residential
Allowance for loan losses
Recoveries	281	333
Non-PCI Loans \| Commercial lending \| Construction and land
Allowance for loan losses
Recoveries	63	435
Non-PCI Loans \| Consumer lending \| Real estate loan \| Single-family residential
Allowance for loan losses
Charge-offs	0	(1)
Recoveries	2	184
Non-PCI Loans \| Consumer lending \| HELOCs
Allowance for loan losses
Recoveries	2	0
Non-PCI Loans \| Consumer lending \| Other consumer
Allowance for loan losses
Charge-offs	(14)	(17)
Recoveries	0	1
PCI Loans
Allowance for loan losses
Beginning balance	22	58
(Reversal of) provision for loan losses	(8)	(11)
Ending balance	14	$ 47
PCI Loans \| Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Beginning balance	0
Ending balance	0
PCI Loans \| Commercial lending \| Commercial real estate (“CRE”)
Allowance for loan losses
Beginning balance	22
Ending balance	14
PCI Loans \| Commercial lending \| Real estate loan \| Multifamily residential
Allowance for loan losses
Beginning balance	0
Ending balance	0
PCI Loans \| Commercial lending \| Construction and land
Allowance for loan losses
Beginning balance	0
Ending balance	0
PCI Loans \| Consumer lending \| Real estate loan \| Single-family residential
Allowance for loan losses
Beginning balance	0
Ending balance	0
PCI Loans \| Consumer lending \| HELOCs
Allowance for loan losses
Beginning balance	0
Ending balance	0
PCI Loans \| Consumer lending \| Other consumer
Allowance for loan losses
Beginning balance	0
Ending balance	$ 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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