v2.4.0.8

Federal Home Loan Bank and Federal Reserve Bank Borrowings (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2013
Debt Instrument [Line Items] |
Schedule of Financial Instruments Owned and Pledged as Collateral | The following table summarizes, as of December 31, 2013 and 2012, the carrying value of securities pledged as collateral to secure public deposits, borrowings and other purposes as permitted or required by law:
|  | December 31, 2013 |  | December 31, 2012
|  | (in thousands)
Washington and Oregon State to secure public deposits |  | $ | 277,012 |  |  | $ | 281,006 |
Federal Reserve Bank to secure borrowings |  | 42,694 |  |  | 47,634 |
Other securities pledged |  | 43,081 |  |  | 46,090 |
Total securities pledged as collateral |  | $ | 362,787 |  |  | $ | 374,730 |
Federal Home Loan Bank Advances [Member] |
Debt Instrument [Line Items] |
Debt Instrument Activity For Year | The maximum, average outstanding and year-end balances and average interest rates on advances from the FHLB were as follows for the years ended December 31, 2013, 2012 and 2011:
|  | Years ended December 31,
|  | 2013 |  | 2012 |  | 2011
|  | (dollars in thousands)
Balance at end of year |  | $ | 36,606 |  |  | $ | 6,644 |  |  | $ | 119,009 |
Average balance during the year |  | $ | 51,030 |  |  | $ | 100,337 |  |  | $ | 120,419 |
Maximum month-end balance during the year |  | $ | 190,631 |  |  | $ | 118,967 |  |  | $ | 127,426 |
Weighted average rate during the year |  | 1.12 | % |  | 2.79 | % |  | 2.76 | %
Weighted average rate at December 31 |  | 1.09 | % |  | 5.42 | % |  | 2.81 | %
Schedule of Financial Instruments Owned and Pledged as Collateral | FHLB advances are collateralized by the following:
|  | December 31,
|  | 2013 |  | 2012
|  | (in thousands)
Recorded value of blanket pledge on loans receivable |  | $ | 1,075,389 |  |  | $ | 443,419 |
Total |  | $ | 1,075,389 |  |  | $ | 443,419 |
FHLB borrowing capacity |  | $ | 1,037,159 |  |  | $ | 435,189 |
Federal Home Loan Bank Fixed Rate Advances [Member] |
Debt Instrument [Line Items] |
Schedule of Maturities of Long-term Debt | At December 31, 2013 FHLB advances were scheduled to mature as follows:
|  | Federal Home Loan Bank Advances Fixed rate advances
|  | Wtd Avg Rate |  | Amount
|  | (dollars in thousands)
Within 1 year |  | 0.23 | % |  | $ | 30,000 |
Over 1 through 5 years |  | 5.66 | % |  | 1,000 |
Due after 10 years |  | 5.37 | % |  | 5,000 |
Total |  | 36,000 |
Valuation adjustment from acquisition accounting |  | 606 |
Total |  | $ | 36,606 |
Federal Reserve Bank Advances [Member] |
Debt Instrument [Line Items] |
Debt Instrument Activity For Year | Although the Company has not had FRB borrowings in the last three years
Schedule of Financial Instruments Owned and Pledged as Collateral | Federal Reserve Bank:
|  | December 31,
|  | 2013 |  | 2012
|  | (in thousands)
Fair value of investment securities |  | $ | 40,210 |  |  | $ | 45,641 |
Recorded value of pledged commercial loans |  | 45,242 |  |  | 13,815 |
Total |  | $ | 85,452 |  |  | $ | 59,456 |
Federal Reserve Bank borrowing capacity |  | $ | 85,452 |  |  | $ | 59,456 |

X
- Definition Debt Instrument Activity For Year [Table Text Block] + References No definition available. + Details
Name: | colb_DebtInstrumentActivityForYearTableTextBlock
Namespace Prefix: | colb_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 50 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=7523297&loc=SL6224234-111729 Reference 2: 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=6467456&loc=d3e113888-111728 + Details
Name: | us-gaap_ScheduleOfFinancialInstrumentsOwnedAndPledgedAsCollateralTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 + Details
Name: | us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration