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Stock Compensation Plans - Weighted Average Grant Date Fair Values of Stock Options and the Assumptions Used (Parenthetical) (Details) - shares | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018
Black-Scholes model assumptions: |  |
Options granted in period (in shares) | 0 | 0

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- References No definition available. + Details
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Balance Type: | na
Period Type: | duration

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- Definition Gross number of share options (or share units) granted during the period. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Period Type: | duration