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Compensation Plans: Stock Based (Details) $ in Millions |  |  | 3 Months Ended | 6 Months Ended
--- | --- | --- | --- | ---
Jul. 01, 2021 shares | Jun. 30, 2021 USD ($) shares | Jun. 30, 2021 USD ($) shares | Jun. 30, 2020 USD ($) | Jun. 30, 2021 USD ($) shares | Jun. 30, 2020 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Shares available for grant |  | 3,800,000 | 3,800,000 |  | 3,800,000 |
Performance Shares (PSUs) |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Award Vesting Period |  | 3 years |  |  |  |
Stock-based compensation expense | $ |  |  | $ 1.3 | $ 2.8 | $ 4.5 | $ 5.4
Unrecognized stock based compensation expense | $ |  | $ 3.0 | $ 3.0 |  | $ 3.0 |
Performance Shares (PSUs) | Minimum [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Multiplier applied to PSU awards at settlement |  | 0 | 0 |  | 0 |
Performance Shares (PSUs) | Maximum [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Multiplier applied to PSU awards at settlement |  | 2 | 2 |  | 2 |
Restricted Stock Units (RSUs) |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Stock-based compensation expense | $ |  |  | $ 2.1 | $ 2.7 | $ 4.3 | $ 5.3
Unrecognized stock based compensation expense | $ |  | $ 10.1 | $ 10.1 |  | $ 10.1 |
Number of shares represented by each RSU |  | 1 | 1 |  | 1 |
Restricted Stock Units (RSUs) | Subsequent Event [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Restricted Stock, Shares Settled Gross of Shares for Tax Withholdings | 349,328 |  |  |  |  |
Shares Issued in Period | 250,009 |  |  |  |  |
Shares Withheld for Tax Withholding Obligation | 99,319 |  |  |  |  |

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