Earnings per Common Share - Calculation of Basic and Diluted Weighted-Average Shares Outstanding (Details) - shares shares in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Weighted-average shares - basic (in shares)	415,514	445,538	463,735
Dilution effect of stock awards at end of period (in shares)	1,937	2,030	1,816
Weighted-average shares - diluted (in shares)	417,451	447,568	465,551

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- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

+ References

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- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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