XML 41 R31.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Accumulated Other Comprehensive Income (Tables) | 9 Months Ended
--- | ---
Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Abstract] |
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] | The following table shows changes in accumulated other comprehensive income (loss) by component for the three and nine month periods ended September 30, 2017 and 2016:
|  | Unrealized Gains and Losses on Available-for-Sale Securities (1) |  | Unrealized Gains and Losses on Pension Plan Liability (1) |  | Total (1)
Three months ended September 30, 2017 |  | (in thousands)
Beginning balance |  | $ | (4,969 | ) |  | $ | (1,559 | ) |  | $ | (6,528 | )
Other comprehensive income before reclassifications |  | 549 |  |  | — |  |  | 549 |
Amounts reclassified from accumulated other comprehensive income |  | — |  |  | 46 |  |  | 46 |
Net current-period other comprehensive income |  | 549 |  |  | 46 |  |  | 595 |
Ending balance |  | $ | (4,420 | ) |  | $ | (1,513 | ) |  | $ | (5,933 | )
Three months ended September 30, 2016 |  |  |  |  |  |
Beginning balance |  | $ | 27,280 |  |  | $ | (6,469 | ) |  | $ | 20,811 |
Other comprehensive loss before reclassifications |  | (4,049 | ) |  | — |  |  | (4,049 | )
Amounts reclassified from accumulated other comprehensive income (loss) |  | (364 | ) |  | 107 |  |  | (257 | )
Net current-period other comprehensive income (loss) |  | (4,413 | ) |  | 107 |  |  | (4,306 | )
Ending balance |  | $ | 22,867 |  |  | $ | (6,362 | ) |  | $ | 16,505 |
Nine months ended September 30, 2017 |  |  |  |  |  |
Beginning balance |  | $ | (12,704 | ) |  | $ | (6,295 | ) |  | $ | (18,999 | )
Other comprehensive income before reclassifications |  | 8,284 |  |  | 4,604 |  |  | 12,888 |
Amounts reclassified from accumulated other comprehensive income |  | — |  |  | 178 |  |  | 178 |
Net current-period other comprehensive income |  | 8,284 |  |  | 4,782 |  |  | 13,066 |
Ending balance |  | $ | (4,420 | ) |  | $ | (1,513 | ) |  | $ | (5,933 | )
Nine months ended September 30, 2016 |  |  |  |  |  |
Beginning balance |  | $ | 386 |  |  | $ | (6,681 | ) |  | $ | (6,295 | )
Other comprehensive income before reclassifications |  | 23,229 |  |  | — |  |  | 23,229 |
Amounts reclassified from accumulated other comprehensive income (loss) |  | (748 | ) |  | 319 |  |  | (429 | )
Net current-period other comprehensive income |  | 22,481 |  |  | 319 |  |  | 22,800 |
Ending balance |  | $ | 22,867 |  |  | $ | (6,362 | ) |  | $ | 16,505 |
__________ (1) All amounts are net of tax. Amounts in parenthesis indicate debits.
Schedule of reclassifications from accumulated other comprehensive income [Table Text Block] | The following table shows details regarding the reclassifications from accumulated other comprehensive income (loss) for the three and nine month periods ended September 30, 2017 and 2016:
|  | Amount Reclassified from Accumulated Other Comprehensive Income (Loss) |  |
|  | Three Months Ended September 30, |  | Nine Months Ended September 30, |  | Affected line Item in the Consolidated
|  | 2017 |  | 2016 |  | 2017 |  | 2016 |  | Statement of Income
|  | (in thousands) |  |
Unrealized gains and losses on available-for-sale securities |  |  |  |  |  |  |  |  |  |
Investment securities gains |  | $ | — |  |  | $ | 572 |  |  | $ | — |  |  | $ | 1,174 |  |  | Investment securities gains, net
|  | — |  |  | 572 |  |  | — |  |  | 1,174 |  |  | Total before tax
|  | — |  |  | (208 | ) |  | — |  |  | (426 | ) |  | Income tax provision
|  | $ | — |  |  | $ | 364 |  |  | $ | — |  |  | $ | 748 |  |  | Net of tax
Amortization of pension plan liability |  |  |  |  |  |  |  |  |  |
Actuarial losses |  | $ | (72 | ) |  | $ | (167 | ) |  | $ | (279 | ) |  | $ | (501 | ) |  | Compensation and employee benefits
|  | (72 | ) |  | (167 | ) |  | (279 | ) |  | (501 | ) |  | Total before tax
|  | 26 |  |  | 60 |  |  | 101 |  |  | 182 |  |  | Income tax benefit
|  | $ | (46 | ) |  | $ | (107 | ) |  | $ | (178 | ) |  | $ | (319 | ) |  | Net of tax

X
- Definition Accumulated Other Comprehensive Income (Loss) [Abstract] + References No definition available. + Details
Name: | colb_AccumulatedOtherComprehensiveIncomeLossAbstract
Namespace Prefix: | colb_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of information about items reclassified out of accumulated other comprehensive income (loss). + References No definition available. + Details
Name: | us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the components of accumulated other comprehensive income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580 + Details
Name: | us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration