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Capital Stock and Dividend Restrictions (Details) $ in Millions |  | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
May 30, 2017 USD ($) shares | Dec. 31, 2018 USD ($) votes shares | Dec. 31, 2017 USD ($) shares | Dec. 31, 2016 USD ($) | Nov. 28, 2018 shares | Jun. 08, 2018 shares | Sep. 25, 2017 USD ($)
Class of Stock |  |  |  |  |  |  |
Common stock, shares authorized |  | 200,000,000 |  |  |  |  |
Aggregate purchase price of shares repurchased and retired | $ |  | $ 1.0 | $ 1.3 | $ 26.9 |  |  |
Class A Common Stock |  |  |  |  |  |  |
Class of Stock |  |  |  |  |  |  |
Common stock, shares authorized |  | 100,000,000 |  |  |  |  |
Common stock, voting rights per share (vote per share) | votes |  | 1 |  |  |  |  |
Common stock, shares, outstanding |  | 38,169,575 | 33,560,202 |  |  |  |
Common shares purchased and retired |  | 0 | 0 |  |  |  |
Class B Common Stock |  |  |  |  |  |  |
Class of Stock |  |  |  |  |  |  |
Common stock, shares authorized |  | 100,000,000 |  |  |  |  |
Common stock, voting rights per share (vote per share) | votes |  | 5 |  |  |  |  |
Common stock, shares, outstanding |  | 22,453,672 | 22,905,357 |  |  |  |
Community 1st Bank [Member] | Class A Common Stock |  |  |  |  |  |  |
Class of Stock |  |  |  |  |  |  |
Common stock, shares authorized |  |  |  |  | 492,069 |  |
Idaho Independent Bank [Member] | Class A Common Stock |  |  |  |  |  |  |
Class of Stock |  |  |  |  |  |  |
Common stock, shares authorized |  |  |  |  | 4,045,302 |  |
Inland Northwest Bank [Member] | Class A Common Stock |  |  |  |  |  |  |
Class of Stock |  |  |  |  |  |  |
Common stock, shares authorized |  |  |  |  |  | 3,982,842 |
Cascade Bank | Class A Common Stock |  |  |  |  |  |  |
Class of Stock |  |  |  |  |  |  |
Common stock issued (in shares) | 3,837,540 |  |  |  |  |  |
Class A common stock | $ | $ 173.3 |  |  |  |  |  |
Board of Directors |  |  |  |  |  |  |
Class of Stock |  |  |  |  |  |  |
Aggregate value of shares issued to directors | $ |  | $ 0.5 | $ 0.5 |  |  |  |
Board of Directors | Class A Common Stock |  |  |  |  |  |  |
Class of Stock |  |  |  |  |  |  |
Shares issued to directors during period |  | 11,389 | 14,926 |  |  |  |
Secondary Public Offering | Class A Common Stock |  |  |  |  |  |  |
Class of Stock |  |  |  |  |  |  |
Common stock, value authorized | $ |  |  |  |  |  |  | $ 250.0

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