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Nature of Operations and Summary of Significant Accounting Policies (Details Textual) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 USD ($) quarter step operating_segment division reporting_unit $ / shares | Dec. 31, 2016 USD ($)
Number of Bank Divisions | division | 14 |
Number of Operating Segments | operating_segment | 1 |
Total assets | $ 9,706,349,000 | $ 9,450,600,000
Gross loans | $ 6,577,824,000 | 5,684,463,000
Maximum Period of Original Maturity to be Included in Cash and Cash Equivalents | 3 months |
Federal Reserve Balance or Cash on Hand Required | $ 10,916,000 |
Minimum Period Past Due to Consider Loans as Delinquent | 30 days |
Minimum Period Past Due to Consider Loans as Non Accrual | 90 days |
Number of Quarters Used to Evaluate Historical Loss Experience | quarter | 12 |
Maximum period up to which purchase price of business is allocated to assets acquired and liabilities assumed | 1 year |
Number of Reporting Units Subsequent to Aggregation for Goodwill Assessment | reporting_unit | 1 |
Number of steps included in goodwill impairment test | step | 2 |
Bank Owned Life Insurance | $ 59,351,000 | $ 50,451,000
Percentage of likelihood for term more likely than not as it relates to income taxes | 50.00% |
Federal Tax Rate Subsequent to Enactment of The Tax Cuts and Jobs Act | 21.00% |
Period to begin developing and implementing processes and procedures for FASB Accounting Standards Update 2016-13 | 2 years |
Maximum lease term to not recognize lease assets and liabilities | 12 months |
Number of Steps to Achieve Core Revenue Recognition Principal | step | 5 |
Accounting Standards Update 2018-02 |  |
Reclassifications from accumulated other comprehensive income (loss) to retained earnings | $ 351,000 |
Accounting Standards Update 2016-09 |  |
Effect of change on net income from applying new accounting pronouncement | $ 553,000 |
Effect of change on diluted earnings per share from applying new accounting pronouncement | $ / shares | $ 0.01 |
Accounting Standards Update 2017-08 |  |
Effect of cumulative change on retained earnings from applying new accounting pronouncement | $ 21,219,000 |
Interest Rate Lock Commitments |  |
Off-balance Sheet Commitments | $ 67,861,000 |
Consumer and Other |  |
Minimum Number of Days Delinquent to Charge Off Loans | 120 days |
Minimum Range |  |
Number of years for home equity loan origination term | 10 years |
Minimum Range | Office Buildings |  |
Useful life of premises and equipment | 15 years |
Minimum Range | Furniture, fixtures and equipment |  |
Useful life of premises and equipment | 3 years |
Maximum Range |  |
Number of years for home equity loan origination term | 15 years |
Maximum Range | Office Buildings |  |
Useful life of premises and equipment | 40 years |
Maximum Range | Furniture, fixtures and equipment |  |
Useful life of premises and equipment | 10 years |
Collegiate Peaks Bank |  |
Total assets | $ 532,958,000 |
Gross loans | 345,687,000 |
Total deposits | 463,970,000 |
First Security Bank |  |
Total assets | 1,027,685,000 |
Gross loans | 639,880,000 |
Total deposits | $ 891,390,000 |

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