Share-Based Compensation (Details 3) (USD $)	12 Months Ended
Dec. 31, 2012 years	Dec. 31, 2011 years	Dec. 31, 2010 years
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions
Weighted-average fair value	$ 18.59	$ 33.92	$ 25.70
Risk-free interest rate	0.90%	2.00%	2.80%
Expected option life	5.0	5.0	5.0
Expected volatility	64.00%	64.10%	64.20%
Dividend yield	0.60%	0.60%	0.60%

The period of time an equity-based award is expected to be outstanding. An equity-based award's expected term is generally determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior.

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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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