Share-Based Compensation (Summary of the Corporation's Stock Option Activity and Related Information) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Shares in treasury	88,997,430	86,069,234
Stock Options
Number of options outstanding at January 1, 2020	2,680,000
Options granted	514,000
Options forfeited or expired	(40,000)
Options exercised	(275,000)
Number of options outstanding at December 31, 2020	2,879,000
Number of options exercisable at December 31, 2020	1,992,000
Options outstanding at January 1, 2020 (Weighted-average exercise price)	$ 49.58
Options granted (Weighted-average exercise price)	61.75
Options forfeited or expired (Weighted-average exercise price)	67.20
Options exercised (Weighted-average exercise price)	35.91
Options outstanding at December 31, 2020 (Weighted-average exercise price)	52.81
Options exercisable at December 31, 2020 (Weighted-average exercise price)	$ 45.20
Weighted-average remaining contractual term in years at December 31, 2020	5 years 3 months 18 days
Weighted-average remaining contractual term in years exercisable at December 31, 2020	4 years
Aggregate intrinsic value outstanding at December 31, 2020	$ 30
Aggregate intrinsic value exercisable at December 31, 2020	$ 29

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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Net number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of share options (or share units) exercised during the current period.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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