Share-based Compensation Assumptions (Details) (Market Based Performance Share Units [Member], Long-Term Compensation Plan - 2013 [Member], USD $)	3 Months Ended
Mar. 31, 2013
Market Based Performance Share Units [Member] \| Long-Term Compensation Plan - 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Date Fair Value per Share	$ 24.74
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	59.50%
Risk-free interest rate	0.38%
Expected life (in years)	2 years 9 months 26 days
Expected dividend yield	0.00%

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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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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