XML 43 R33.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Derivatives and Hedging Activities (Tables) | 6 Months Ended
--- | ---
Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract] |
Schedule of Notional Amounts and Estimated Fair Values of Derivatives | The notional amounts and estimated fair values of the Company's derivatives are presented in the following table. Fair value estimates are obtained from third parties and are based on pricing models.
| June 30, 2018 |  | December 31, 2017
| Notional Amount | Estimated Fair Value |  | Notional Amount | Estimated Fair Value
Derivative Assets (included in other assets on the consolidated balance sheets):
Non-hedging interest rate derivatives: |  |  |  |  |
Interest rate swap contracts | $ | 389.8 |  | $ | 10.1 |  |  | $ | 344.2 |  | $ | 7.5 |
Interest rate lock commitments | 73.7 |  | 1.7 |  |  | 60.7 |  | 1.3 |
Total derivative assets | $ | 463.5 |  | $ | 11.8 |  |  | $ | 404.9 |  | $ | 8.8 |
Derivative Liabilities (included in accounts payable and accrued expenses on the consolidated balance sheets):
Non-hedging interest rate derivatives: |  |  |  |  |
Interest rate swap contracts | $ | 389.8 |  | $ | 9.3 |  |  | $ | 344.2 |  | $ | 7.8 |
Forward loan sales contracts | 102.3 |  | 0.4 |  |  | 88.8 |  | 0.1 |
Total derivative liabilities | $ | 492.1 |  | $ | 9.7 |  |  | $ | 433.0 |  | $ | 7.9 |
Offsetting Assets and Liabilities | The following table illustrates the potential effect of the Company's master netting arrangements, by type of financial instrument, on the Company's consolidated balance sheets as of June 30, 2018 and December 31, 2017:
| June 30, 2018
| Gross Amounts Recognized |  | Gross Amounts Offset in the Balance Sheet |  | Net Amounts in the Balance Sheet |  | Financial Instruments |  | Fair Value of Financial Collateral in the Balance Sheet |  | Net Amount
Financial Assets
Interest rate swap contracts | $ | 10.1 |  |  | $ | — |  |  | $ | 10.1 |  |  | $ | 1.1 |  |  | $ | 1.9 |  |  | $ | 7.1 |
Mortgage related derivatives | 1.7 |  |  | — |  |  | 1.7 |  |  | — |  |  | — |  |  | 1.7 |
Total derivatives | 11.8 |  |  | — |  |  | 11.8 |  |  | 1.1 |  |  | 1.9 |  |  | 8.8 |
Total assets | $ | 11.8 |  |  | $ | — |  |  | $ | 11.8 |  |  | $ | 1.1 |  |  | $ | 1.9 |  |  | $ | 8.8 |
Financial Liabilities
Interest rate swap contracts | $ | 9.3 |  |  | $ | — |  |  | $ | 9.3 |  |  | $ | 1.1 |  |  | $ | 7.4 |  |  | $ | 0.8 |
Mortgage related derivatives | 0.4 |  |  | — |  |  | 0.4 |  |  | — |  |  | — |  |  | 0.4 |
Total derivatives | 9.7 |  |  | — |  |  | 9.7 |  |  | 1.1 |  |  | 7.4 |  |  | 1.2 |
Repurchase agreements | 641.8 |  |  | — |  |  | 641.8 |  |  | — |  |  | 641.8 |  |  | — |
Total liabilities | $ | 651.5 |  |  | $ | — |  |  | $ | 651.5 |  |  | $ | 1.1 |  |  | $ | 649.2 |  |  | $ | 1.2 |
| December 31, 2017
| Gross Amounts Recognized |  | Gross Amounts Offset in the Balance Sheet |  | Net Amounts in the Balance Sheet |  | Financial Instruments |  | Fair Value of Financial Collateral in the Balance Sheet |  | Net Amount
Financial Assets
Interest rate swap contracts | $ | 7.5 |  |  | $ | — |  |  | $ | 7.5 |  |  | $ | 2.4 |  |  | $ | — |  |  | $ | 5.1 |
Mortgage related derivatives | 1.3 |  |  | — |  |  | 1.3 |  |  | — |  |  | — |  |  | 1.3 |
Total derivatives | 8.8 |  |  | — |  |  | 8.8 |  |  | 2.4 |  |  | — |  |  | 6.4 |
Total assets | $ | 8.8 |  |  | $ | — |  |  | $ | 8.8 |  |  | $ | 2.4 |  |  | $ | — |  |  | $ | 6.4 |
Financial Liabilities
Interest rate swap contracts | $ | 7.8 |  |  | $ | — |  |  | $ | 7.8 |  |  | $ | 2.4 |  |  | $ | 3.3 |  |  | $ | 2.1 |
Mortgage related derivatives | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | — |  |  | 0.1 |
Total derivatives | 7.9 |  |  | — |  |  | 7.9 |  |  | 2.4 |  |  | 3.3 |  |  | 2.2 |
Repurchase agreements | 643.0 |  |  | — |  |  | 643.0 |  |  | — |  |  | 643.0 |  |  | — |
Total liabilities | $ | 650.9 |  |  | $ | — |  |  | $ | 650.9 |  |  | $ | 2.4 |  |  | $ | 646.3 |  |  | $ | 2.2 |
Schedule of Derivative Instruments, Effect on Other Comprehensive Income (Loss) | The following table presents the pre-tax gains or losses related to derivative contracts that were recorded in other non-interest income in the Company's statements of income for the periods indicated:
| Three Months Ended June 30, |  | Six Months Ended June 30,
| 2018 | 2017 |  | 2018 | 2017
Derivatives designated as hedges: |  |  |  |  |
Amount of loss recognized in other comprehensive income (effective portion) | $ | — |  | $ | (0.5 | ) |  | $ | — |  | $ | (0.4 | )
Non-hedging interest rate derivatives: |  |  |  |  |
Amount of gain recognized in other non-interest income | 0.1 |  | 0.1 |  |  | 0.3 |  | — |
Amount of net fee income recognized in other non-interest income | 0.4 |  | 0.3 |  |  | 0.9 |  | 0.3 |
Amount of net gains recognized in mortgage banking revenues | 0.1 |  | 0.3 |  |  | — |  | 0.2 |

X
- Definition Offsetting Assets and Liabilities [Table Text Block] + References No definition available. + Details
Name: | fibk_OffsettingAssetsandLiabilitiesTableTextBlock
Namespace Prefix: | fibk_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the effective portion of the gains and losses on derivative instruments designated (and non-derivative instruments) designated and qualifying in cash flow hedges and net investment hedges that was recognized in other comprehensive income (loss) during the current period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959 + Details
Name: | us-gaap_ScheduleOfDerivativeInstrumentsEffectOnOtherComprehensiveIncomeLossTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of interest rate derivatives, including, but not limited to, the fair value of the derivatives, statement of financial position location, and statement of financial performance location of these instruments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959 + Details
Name: | us-gaap_ScheduleOfInterestRateDerivativesTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration