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Assumptions Used to Estimate Fair Value of Stock Options and Stock Appreciation Rights Awards (Detail)
3 Months Ended 6 Months Ended
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]      
Risk free interest rate, minimum     1.19%
Risk free interest rate, maximum     1.51%
Risk free interest rate 1.19% 0.64%  
Expected volatility 57.60% 57.60% 57.60%
Expected lives (years) 4 years 4 years 4 years
Expected dividend yield 0.00% 0.00% 0.00%