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Share-Based Payments - Table 1 (Details)	12 Months Ended
Share-Based Payments - Table 1 (Details)	Dec. 31, 2011 Y	Dec. 31, 2010 Y	Dec. 31, 2009 Y
Schedule of Weighted Average Assumptions Used to Determine Fair Value of Stock Options
Expected volatility	41.50%	44.70%	45.00%
Risk-free interest rate	2.80%	3.10%	2.70%
Expected life (years)	6.7	6.7	6.5
Dividend yield	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.

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