v2.4.0.8

Fair Value Accounting and Measurement (Financial Assets Accounted For Fair Value On Nonrecurring Basis) (Details) (Fair Value, Measurements, Nonrecurring [Member], USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2013 | Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | $ 8,973 | $ 10,599
Non-Covered Other Real Estate Owned Fair Value | 5,080 | 10,970
Other Real Estate Owned, Fair Value Disclosure | 613 | 2,663
Other Personal Property Owned, Fair Value Disclosure |  | 210
Assets, Fair Value Disclosure | 14,666 | 24,442
Losses During Period | 2,766 | 8,750
Fair Value, Inputs, Level 1 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Non-Covered Other Real Estate Owned Fair Value | 0 | 0
Other Real Estate Owned, Fair Value Disclosure | 0 | 0
Other Personal Property Owned, Fair Value Disclosure |  | 0
Assets, Fair Value Disclosure | 0 | 0
Fair Value, Inputs, Level 2 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Non-Covered Other Real Estate Owned Fair Value | 0 | 0
Other Real Estate Owned, Fair Value Disclosure | 0 | 0
Other Personal Property Owned, Fair Value Disclosure |  | 0
Assets, Fair Value Disclosure | 0 | 0
Fair Value, Inputs, Level 3 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 8,973 | 10,599
Non-Covered Other Real Estate Owned Fair Value | 5,080 | 10,970
Other Real Estate Owned, Fair Value Disclosure | 613 | 2,663
Other Personal Property Owned, Fair Value Disclosure |  | 210
Assets, Fair Value Disclosure | 14,666 | 24,442
Covered Loans [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Losses During Period | 236 | 1,032
Impaired Loans [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Losses During Period | 1,536 | 3,891
Other Personal Property Owned [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Losses During Period |  | 39
Noncovered Loans [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Losses During Period | $ 994 | $ 3,788

X
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Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Non-Covered Other Real Estate Owned Fair Value + References No definition available. + Details
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Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Other Personal Property Owned, Fair Value Disclosure + References No definition available. + Details
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Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Other Real Estate Owned, Fair Value Disclosure + References No definition available. + Details
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Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258 + Details
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- Details
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- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 30 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14172-108612 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
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Period Type: | duration