Stock-Based Compensation (Performance Stock Units Assumptions) (Details) - $ / shares	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Share Based Payment Award Performance Share Units Valuation Assumptions [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	1.40%	2.50%	2.70%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	5 years	5 years	5 years
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	29.40%	28.90%	27.60%
Performance Shares [Member]
Schedule Of Share Based Payment Award Performance Share Units Valuation Assumptions [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	1.40%	2.50%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	2 years 10 months 17 days	2 years 10 months 17 days
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	32.00%	30.30%
Share Base Compensation Average Correlation Coefficient of Peer Companies	0.49	0.49
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 74.61	$ 114.38
Minimum [Member] \| Performance Shares [Member]
Schedule Of Share Based Payment Award Performance Share Units Valuation Assumptions [Line Items]
Share Based Compensation Arrangements Expected Volatility Rate of Peer Companies	15.70%	14.50%
Maximum [Member] \| Performance Shares [Member]
Schedule Of Share Based Payment Award Performance Share Units Valuation Assumptions [Line Items]
Share Based Compensation Arrangements Expected Volatility Rate of Peer Companies	47.40%	47.80%

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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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

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
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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- Definition

[Line Items] for Tabular disclosure of the significant assumptions used during the year to estimate the fair value of performance share units, including but not limited to volatility of common stock, volatility of peer companies average coefficient of peer companies and risk- free interest rate.

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No definition available.

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- Definition

Share Base Compensation Average Correlation Coefficient of Peer Companies

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- Definition

Share Based Compensation Arrangements Expected Volatility Rate of Peer Companies

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