XML 53 R38.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Securities (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items] |
Securities Available for Sale | The following table summarizes the amortized cost, gross unrealized gains and losses and the resulting fair value of securities available for sale:
|  | Amortized Cost |  | Gross Unrealized Gains |  | Gross Unrealized Losses |  | Fair Value
December 31, 2016 |  | (in thousands)
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations |  | $ | 1,486,690 |  |  | $ | 2,760 |  |  | $ | (23,718 | ) |  | $ | 1,465,732 |
State and municipal securities |  | 473,914 |  |  | 6,343 |  |  | (5,197 | ) |  | 475,060 |
U.S. government agency and government-sponsored enterprise securities |  | 332,348 |  |  | 1,065 |  |  | (1,511 | ) |  | 331,902 |
U.S. government securities |  | 801 |  |  | — |  |  | (1 | ) |  | 800 |
Other securities |  | 5,284 |  |  | 63 |  |  | (264 | ) |  | 5,083 |
Total |  | $ | 2,299,037 |  |  | $ | 10,231 |  |  | $ | (30,691 | ) |  | $ | 2,278,577 |
December 31, 2015 |  |  |  |  |  |  |  |
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations |  | $ | 1,296,955 |  |  | $ | 4,525 |  |  | $ | (14,991 | ) |  | $ | 1,286,489 |
State and municipal securities |  | 480,417 |  |  | 12,690 |  |  | (938 | ) |  | 492,169 |
U.S. government agency and government-sponsored enterprise securities |  | 354,515 |  |  | 1,113 |  |  | (1,846 | ) |  | 353,782 |
U.S. government securities |  | 20,439 |  |  | — |  |  | (302 | ) |  | 20,137 |
Other securities |  | 5,284 |  |  | 24 |  |  | (191 | ) |  | 5,117 |
Total |  | $ | 2,157,610 |  |  | $ | 18,352 |  |  | $ | (18,268 | ) |  | $ | 2,157,694 |
Schedule of gross realized gains and losses on sales and calls of securities available for sale [Table Text Block] | The following table provides the gross realized gains and losses on the sales and calls of securities for the periods indicated:
|  | Years Ended December 31,
|  | 2016 |  | 2015 |  | 2014
|  | (in thousands)
Gross realized gains |  | $ | 1,181 |  |  | $ | 1,591 |  |  | $ | 553 |
Gross realized losses |  | — |  |  | (10 | ) |  | (1 | )
Net realized gains |  | $ | 1,181 |  |  | $ | 1,581 |  |  | $ | 552 |
Schedule of Contractual Maturities of Investment Securities Available for Sale | The scheduled contractual maturities of investment securities available for sale at December 31, 2016 are presented as follows:
|  | December 31, 2016
|  | Amortized Cost |  | Fair Value
|  | (in thousands)
Due within one year |  | $ | 38,596 |  |  | $ | 38,717 |
Due after one year through five years |  | 515,056 |  |  | 517,283 |
Due after five years through ten years |  | 679,739 |  |  | 672,018 |
Due after ten years |  | 1,060,362 |  |  | 1,045,476 |
Other securities with no stated maturity |  | 5,284 |  |  | 5,083 |
Total investment securities available-for-sale |  | $ | 2,299,037 |  |  | $ | 2,278,577 |
Schedule of Securities pledged as collateral [Table Text Block] | The following table summarizes the carrying value of securities pledged as collateral to secure public deposits, borrowings and other purposes as permitted or required by law:
|  | December 31, 2016 |  | December 31, 2015
|  | (in thousands)
Washington and Oregon State to secure public deposits |  | $ | 232,714 |  |  | $ | 341,079 |
Federal Reserve Bank to secure borrowings |  | 33,825 |  |  | 48,714 |
Other securities pledged |  | 132,350 |  |  | 143,606 |
Total securities pledged as collateral |  | $ | 398,889 |  |  | $ | 533,399 |
Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses | The following tables show the gross unrealized losses and fair value of the Company’s investments with unrealized losses that are not deemed to be other-than-temporarily impaired, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position at December 31, 2016 and 2015:
|  | Less than 12 Months |  | 12 Months or More |  | Total
|  | Fair Value |  | Unrealized Losses |  | Fair Value |  | Unrealized Losses |  | Fair Value |  | Unrealized Losses
December 31, 2016 |  | (in thousands)
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations |  | $ | 1,029,116 |  |  | $ | (18,788 | ) |  | $ | 159,046 |  |  | $ | (4,930 | ) |  | $ | 1,188,162 |  |  | (23,718 | )
State and municipal securities |  | 211,342 |  |  | (5,064 | ) |  | 3,384 |  |  | (133 | ) |  | 214,726 |  |  | (5,197 | )
U.S. government agency and government-sponsored enterprise securities |  | 218,811 |  |  | (1,511 | ) |  | — |  |  | — |  |  | 218,811 |  |  | (1,511 | )
U.S. government securities |  | 251 |  |  | (1 | ) |  | — |  |  | — |  |  | 251 |  |  | (1 | )
Other securities |  | 2,263 |  |  | (51 | ) |  | 2,743 |  |  | (213 | ) |  | 5,006 |  |  | (264 | )
Total |  | $ | 1,461,783 |  |  | $ | (25,415 | ) |  | $ | 165,173 |  |  | $ | (5,276 | ) |  | $ | 1,626,956 |  |  | $ | (30,691 | )
December 31, 2015 |  |  |  |  |  |  |  |  |  |  |  |
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations |  | $ | 664,509 |  |  | $ | (7,610 | ) |  | $ | 214,325 |  |  | $ | (7,381 | ) |  | $ | 878,834 |  |  | $ | (14,991 | )
State and municipal securities |  | 48,261 |  |  | (358 | ) |  | 31,383 |  |  | (580 | ) |  | 79,644 |  |  | (938 | )
U.S. government agency and government-sponsored enterprise securities |  | 193,400 |  |  | (1,128 | ) |  | 40,034 |  |  | (718 | ) |  | 233,434 |  |  | (1,846 | )
U.S. government securities |  | 10,343 |  |  | (136 | ) |  | 9,794 |  |  | (166 | ) |  | 20,137 |  |  | (302 | )
Other securities |  | 2,300 |  |  | (15 | ) |  | 2,780 |  |  | (176 | ) |  | 5,080 |  |  | (191 | )
Total |  | $ | 918,813 |  |  | $ | (9,247 | ) |  | $ | 298,316 |  |  | $ | (9,021 | ) |  | $ | 1,217,129 |  |  | $ | (18,268 | )

X
- Definition Schedule of amortized cost and fair value of the debt securities available for sale portfolio of the entity by contractual maturity. The table includes maturity categories of: due in one year or less; due after one year through five years; due after five years through ten years; and due after ten years. A single line item is provided for "total securities with no stated maturity" in order for the total line item of the table to match total available for sale securities. + References No definition available. + Details
Name: | colb_ScheduleOfContractualMaturitiesTextBlock
Namespace Prefix: | colb_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Schedule reflecting the gross unrealized losses and fair values of the entity's investments, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position as of the date presented. + References No definition available. + Details
Name: | colb_ScheduleOfGrossUnrealizedLossesAndFairValuesOfSecuritiesInContinuousUnrealizedLossPositionTextBlock
Namespace Prefix: | colb_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition [Table Text Block] for Schedule of Securities pledged as collateral [Table] + References No definition available. + Details
Name: | colb_ScheduleofSecuritiespledgedascollateralTableTextBlock
Namespace Prefix: | colb_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition [Table Text Block] for Schedule of gross realized gains and losses on sales and calls of securities available for sale [Table] + References No definition available. + Details
Name: | colb_ScheduleofgrossrealizedgainsandlossesonsalesandcallsofsecuritiesavailableforsaleTableTextBlock
Namespace Prefix: | colb_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 320 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27337-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27198-111563 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 320 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62586-112803 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27357-111563 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27290-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration