Stock-based Employee Incentive Plans - Valuation and Assumptions (Details) - $ / shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Stock Options and Stock Appreciation Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	2.76%	2.56%	1.62%
Expected volatility	21.27%	18.39%	17.22%
Risk-free interest rate	2.77%	1.77%	1.24%
Expected life (in years)	4 years 9 months 18 days	4 years 1 month 6 days	4 years 2 months 12 days
Weighted-average grant date fair value (in dollars per share)	$ 24.55	$ 9.43	$ 13.00
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	1.45%	1.24%	0.88%
Expected volatility	28.02%	22.70%	20.64%
Risk-free interest rate	1.87%	0.86%	0.45%
Expected life (in years)	15 days	15 days	15 days
Weighted-average grant date fair value (in dollars per share)	$ 12.26	$ 13.01	$ 14.98

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 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 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

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.

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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
-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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