Loans Receivable and Allowance for Credit Losses (Summary of Activities in Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for loan losses
Allowance, beginning of period	$ 260,520	$ 264,959
Gross charge-offs	(473)	(1,900)	$ (5,100)
Allowance, end of period	287,128	260,520	264,959
Commercial Lending \| C&I
Allowance for loan losses
Allowance, beginning of period	142,167
Allowance, end of period	163,058	142,167
Commercial Lending \| CRE
Allowance for loan losses
Allowance, beginning of period	47,927
Allowance, end of period	41,237	47,927
Commercial Lending \| Residential loan \| Multifamily
Allowance for loan losses
Allowance, beginning of period	17,543
Allowance, end of period	19,109	17,543
Commercial Lending \| Construction and land
Allowance for loan losses
Allowance, beginning of period	24,989
Allowance, end of period	26,881	24,989
Consumer Lending \| Residential loan \| Single-family
Allowance for loan losses
Allowance, beginning of period	19,795
Allowance, end of period	26,362	19,795
Consumer Lending \| HELOCs
Allowance for loan losses
Allowance, beginning of period	7,506
Allowance, end of period	7,354	7,506
Consumer Lending \| Other consumer
Allowance for loan losses
Allowance, beginning of period	593
Allowance, end of period	3,127	593
Non-PCI impaired loans
Allowance for loan losses
Allowance, beginning of period	260,402	264,600	260,965
Provision for (reversal of) on loans	49,129	31,959	6,924
Gross charge-offs	(38,975)	(48,508)	(24,254)
Gross recoveries	16,514	12,351	20,965
Net charge-offs	(22,461)	(36,157)	(3,289)
Allowance, end of period	287,070	260,402	264,600
Non-PCI impaired loans \| Commercial Lending \| C&I
Allowance for loan losses
Gross charge-offs	(38,118)	(47,739)	(20,423)
Gross recoveries	12,065	8,453	8,782
Non-PCI impaired loans \| Commercial Lending \| CRE
Allowance for loan losses
Gross charge-offs	0	(464)	(1,052)
Gross recoveries	2,111	1,488	2,488
Non-PCI impaired loans \| Commercial Lending \| Residential loan \| Multifamily
Allowance for loan losses
Gross charge-offs	(635)	(29)	(1,650)
Gross recoveries	1,357	1,476	4,298
Non-PCI impaired loans \| Commercial Lending \| Construction and land
Allowance for loan losses
Gross charge-offs	(149)	(117)	(493)
Gross recoveries	259	203	4,647
Non-PCI impaired loans \| Consumer Lending \| Residential loan \| Single-family
Allowance for loan losses
Gross charge-offs	(1)	(137)	(36)
Gross recoveries	546	401	323
Non-PCI impaired loans \| Consumer Lending \| HELOCs
Allowance for loan losses
Gross charge-offs	(55)	(9)	(98)
Gross recoveries	24	7	54
Non-PCI impaired loans \| Consumer Lending \| Other consumer
Allowance for loan losses
Gross charge-offs	(17)	(13)	(502)
Gross recoveries	152	323	373
PCI Loans
Allowance for loan losses
Allowance, beginning of period	118	359	714
Provision for (reversal of) on loans	(60)	(241)	(355)
Allowance, end of period	58	118	$ 359
PCI Loans \| Commercial Lending \| C&I
Allowance for loan losses
Allowance, beginning of period	1
Allowance, end of period	0	1
PCI Loans \| Commercial Lending \| CRE
Allowance for loan losses
Allowance, beginning of period	112
Allowance, end of period	58	112
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	5
Allowance, end of period	0	5
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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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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.

+ References

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- Definition

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

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