Stock-Based Compensation - Assumptions Used in Options Pricing Model (Details)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Arrangement [Abstract]
Average option life	6 years 6 months	6 years 6 months	6 years
Future dividend yield (as a percentage)	3.88%	2.28%	1.79%
Historical share price volatility (as a percentage)	0.266%	0.282%	0.287%
Weighted-average risk-free interest rate (as a percentage)	2.50%	2.80%	2.10%

No definition available.

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- Definition

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

+ References

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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 expected term of a nonvested share or option award issued to other than an employee.

+ References

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- Definition

The estimated measure of the percentage amount by which a share price is expected to fluctuate during the expected term of a nonvested share or option award issued to other than an employee.

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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=116856206&loc=d3e5070-113901

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-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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