XML 73 R58.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Summary of Significant Accounting Policies (Details) | 12 Months Ended
--- | ---
Dec. 31, 2016 USD ($) location
Accounting Policies [Line Items] |
Number Of Branch Locations | 143
Number Of Days Used To Determine Treatment As Cash Equivalent | 90 days
Number of Days of Delinqunecy at Which Loans Are Categorized As Non Accrual Status | 90 days
Loans and Leases Receivable, Nonaccrual Loans Considered Impaired | $ | $ 500,000
Loans and Leases Receivable, Loans Evaluated For Impairment On Quarterly Basis, Outstanding | $ | $ 500,000
Core Deposits [Member] |
Accounting Policies [Line Items] |
Estimated life of CDI, in years | 10 years
WASHINGTON |
Accounting Policies [Line Items] |
Number Of Branch Locations | 73
OREGON |
Accounting Policies [Line Items] |
Number Of Branch Locations | 56
IDAHO |
Accounting Policies [Line Items] |
Number Of Branch Locations | 14
Vehicles [Member] |
Accounting Policies [Line Items] |
Property, Plant and Equipment, Estimated Useful Lives | P5Y
Minimum [Member] | Building and Building Improvements [Member] |
Accounting Policies [Line Items] |
Property, Plant and Equipment, Estimated Useful Lives | P5Y
Minimum [Member] | Furniture and Fixtures [Member] |
Accounting Policies [Line Items] |
Property, Plant and Equipment, Estimated Useful Lives | P3Y
Minimum [Member] | Software [Member] |
Accounting Policies [Line Items] |
Property, Plant and Equipment, Estimated Useful Lives | P3Y
Maximum [Member] | Building and Building Improvements [Member] |
Accounting Policies [Line Items] |
Property, Plant and Equipment, Estimated Useful Lives | P39Y
Maximum [Member] | Furniture and Fixtures [Member] |
Accounting Policies [Line Items] |
Property, Plant and Equipment, Estimated Useful Lives | P7Y
Maximum [Member] | Software [Member] |
Accounting Policies [Line Items] |
Property, Plant and Equipment, Estimated Useful Lives | P5Y

X
- Definition Accounting Policies [Line Items] + References No definition available. + Details
Name: | colb_AccountingPoliciesLineItems
Namespace Prefix: | colb_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Loans and Leases Receivable, Loans Evaluated For Impairment On Quarterly Basis, Outstanding + References No definition available. + Details
Name: | colb_LoansAndLeasesReceivableLoansEvaluatedForImpairmentOnQuarterlyBasisOutstanding
Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Loans and Leases Receivable, Nonaccrual Loans Considered Impaired + References No definition available. + Details
Name: | colb_LoansAndLeasesReceivableNonaccrualLoansConsideredImpaired
Namespace Prefix: | colb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number Of Branch Locations + References No definition available. + Details
Name: | colb_NumberOfBranchLocations
Namespace Prefix: | colb_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of Days of Delinqunecy at Which Loans Are Categorized As Non Accrual Status + References No definition available. + Details
Name: | colb_NumberOfDaysOfDelinqunecyAtWhichLoansAreCategorizedAsNonAccrualStatus
Namespace Prefix: | colb_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number Of Days Used To Determine Treatment As Cash Equivalent + References No definition available. + Details
Name: | colb_NumberOfDaysUsedToDetermineTreatmentAsCashEquivalent
Namespace Prefix: | colb_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Describes the periods of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=68058157&loc=d3e18780-107790 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 35 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=68071081&loc=d3e1205-110223 + Details
Name: | us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CoreDepositsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=stpr_WA
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=stpr_OR
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=stpr_ID
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_VehiclesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingAndBuildingImprovementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_FurnitureAndFixturesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_ComputerSoftwareIntangibleAssetMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |