Capital Stock (Details)	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Maximum [Member]
Weighted average fair value of common share granted to employees
Expected option life (in years)	5.14	5.33	5.14	5.39
Maximum [Member] \| Stock Option Plan [Member]
Weighted average fair value of common share granted to employees
Annual termination probability	8.31%	9.69%	8.49%	9.69%
Minimum [Member]
Weighted average fair value of common share granted to employees
Expected option life (in years)	1.78	2.99	1.78	2.99
Minimum [Member] \| Stock Option Plan [Member]
Weighted average fair value of common share granted to employees
Annual termination probability	0.00%	0.00%	0.00%	0.00%
Stock Option Plan [Member]
Weighted average fair value of common share granted to employees
Average risk-free interest rate	2.34%	3.09%	2.79%	3.11%
Expected volatility	50.00%	61.00%	50.00%	61.00%
Dividend yield	0.00%	0.00%	0.00%	0.00%

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.

+ References+ Details

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.

+ References+ Details