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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Capital Stock (Details 3)	3 Months Ended		6 Months Ended			12 Months Ended	3 Months Ended		6 Months Ended			12 Months Ended	6 Months Ended	12 Months Ended
Capital Stock (Details 3)	Jun. 30, 2011 Maximum [Member]	Jun. 30, 2010 Maximum [Member]	Jun. 30, 2011 Maximum [Member]	Jun. 30, 2010 Maximum [Member]	Jun. 30, 2011 Maximum [Member] Stock appreciation rights [Member]	Dec. 31, 2010 Maximum [Member] Stock appreciation rights [Member]	Jun. 30, 2011 Minimum [Member]	Jun. 30, 2010 Minimum [Member]	Jun. 30, 2011 Minimum [Member]	Jun. 30, 2010 Minimum [Member]	Jun. 30, 2011 Minimum [Member] Stock appreciation rights [Member]	Dec. 31, 2010 Minimum [Member] Stock appreciation rights [Member]	Jun. 30, 2011 Stock appreciation rights [Member]	Dec. 31, 2010 Stock appreciation rights [Member]
Fair value measurement of stock appreciation rights
Average risk-free interest rate													2.25%	0.65%
Expected option life (in years)	5.14	5.33	5.14	5.39	2.40	2.51	1.78	2.99	1.78	2.99	0.36	0.24
Expected volatility						61.00%						50.00%	50.00%
Annual termination probability					8.31%	8.31%						0.00%
Dividend yield													0.00%	0.00%