Stock Compensation Plans, Weighted Average Assumptions Used in Valuing Stock Options Granted (Details) - Stock Options [Member]	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Weighted average assumptions used in valuing stock options [Abstract]
Risk-free interest rate	1.42%	2.47%	2.57%
Expected dividend yield	0.00%	0.00%	0.00%
Expected life	5 years	5 years	5 years
Expected price volatility	10.18%	11.86%	14.44%

No definition available.

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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

Rate of weighted-average expected volatility for award under share-based payment arrangement.

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- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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