Earnings Per Common Share and Share Awards Share-Based Assumptions (Details)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility	29.40%	30.20%
Interest rate	0.70%	2.30%
Yield rate	1.20%	1.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life in years	6 years 2 months 12 days	7 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life in years	7 years	7 years

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.

+ References

+ Details

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- Definition

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

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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