Equity Option Valuation Assumptions (Details) - $ / shares |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Valuation Assumptions [Abstract] | |||
| Expected period that options will be outstanding (in years) | 5 years 7 days | 4 years 10 months 13 days | 4 years 10 months 25 days |
| Interest rate (based on U.S. Treasury yields at the time of grant) | 1.62% | 1.62% | 1.06% |
| Volatility | 28.75% | 34.67% | 43.22% |
| Dividend yield | 0.00% | 0.00% | 0.00% |
| Weighted-average fair value of options granted | $ 11.87 | $ 22.65 | $ 18.07 |
| X | ||||||||||
- Definition Valuation Assumptions [Abstract] 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 The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. 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
|