Share-Based Payments (Weighted Average Grant Date Assumptions Used in Binomial Optional Valuation Model) (Details) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |||
| Expected volatility | 35.29% | 38.36% | 34.67% |
| Expected dividend yield | 2.84% | 3.92% | 3.00% |
| Expected term | 5 years 7 months 5 days | 5 years 7 months 10 days | 5 years 6 months 26 days |
| Risk-free interest rate | 2.06% | 1.25% | 1.61% |
| X | ||||||||||
- References No definition available.
|
| X | ||||||||||
- 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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- 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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|