Investment Securities (Investment Securities Pledged To Secure Borrowings And Public Deposits) (Details) $ in Thousands	Sep. 30, 2017 USD ($)
Investments, Debt and Equity Securities [Abstract]
To Federal Home Loan Bank to secure borrowings, amortized cost	$ 458
To state and local governments to secure public deposits, amortized cost	926,917
Other securities pledged principally to secure repurchase agreements, amortized cost	426,540
Total pledged securities, amortized cost	1,353,915
To Federal Home Loan Bank to secure borrowings, fair value	467
To state and local governments to secure public deposits, fair value	927,182
Pledged Assets Separately Reported Other Securities Pledged At Fair Value	423,854
Total pledged securities, fair value	$ 1,351,503

Pledged Assets Not Separately Reported Securities Pledged For State and Local Governments

No definition available.

Name:	umpq_PledgedAssetsNotSeparatelyReportedSecuritiesPledgedForStateAndLocalGovernments
Namespace Prefix:	umpq_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Pledged Assets Separately Reported Securities Pledged For State and Local Governments At Fair Value

+ References

No definition available.

+ Details

Name:	umpq_PledgedAssetsSeparatelyReportedSecuritiesPledgedForStateAndLocalGovernmentsAtFairValue
Namespace Prefix:	umpq_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying amount, as of the date of the latest financial statement presented, of other assets which are owned but transferred to serve as collateral for the payment of the related debt obligation, primarily a secured borrowing or repurchase agreement, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

+ Details

Name:	us-gaap_PledgedAssetsNotSeparatelyReportedOtherFinancialInstruments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The sum of the fair values, as of the date of each statement of financial position presented, of assets which are owned but transferred to serve as collateral for the payment of debt obligations, primarily secured borrowings, repurchase agreements or other current or potential obligations, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

+ Details

Name:	us-gaap_PledgedAssetsSeparatelyReportedOnStatementOfFinancialPositionAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The sum of the fair values, as of the date of each statement of financial position presented, of securities that are restricted as collateral for the payment of related debt obligations, primarily secured borrowings and repurchase agreements, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

+ References

+ Details

Name:	us-gaap_PledgedAssetsSeparatelyReportedSecuritiesPledgedAsCollateralAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The fair value, as of the date of each statement of financial position presented, of securities which are owned but transferred to serve as collateral for the payment of the FHLB debt obligations, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

+ References

+ Details

Name:	us-gaap_PledgedAssetsSeparatelyReportedSecuritiesPledgedForFederalHomeLoanBankAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The carrying amount as of the date of the latest financial statement presented of securities which are owned but transferred to serve as collateral for FHLB debt obligations, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

+ References

+ Details

Name:	us-gaap_PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesForFederalHomeLoanBank
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ References

+ Details

Name:	us-gaap_PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesPledged
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant