Quarterly report pursuant to Section 13 or 15(d)

Schedule of Disclosure of Share-based Compensation Arrangements by Share-based Payment Award (Details)

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Schedule of Disclosure of Share-based Compensation Arrangements by Share-based Payment Award (Details) (USD $)
 3 Months Ended 12 Months Ended
Mar. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Weighted Average Remaining Contractual Life - Years 4 years 7 months 2 days 4 years 10 months 2 days  
Number of options outstanding 1,639,842 1,639,842 1,674,065
Weighted Average Exercise Price Stock Options Outstanding $ 11.46 $ 11.46 $ 11.37
Number of Awards Vested 1,588,685 1,523,536  
Weighted Average Exercise Price $ 11.64 $ 11.82  
Weighted Average Remaining Contractual Life of Stock Options Vested 4 years 5 months 26 days 4 years 7 months 13 days  
Range 1 [Member]
      
Exercise price lower range limit $ 4.50 $ 4.50  
Exercise price upper range limit $ 8.70 $ 8.70  
Weighted Average Remaining Contractual Life - Years 6 years 7 days 6 years 3 months 7 days  
Number of options outstanding 844,801 844,801  
Weighted Average Exercise Price Stock Options Outstanding $ 6.33 $ 6.33  
Number of Awards Vested 793,644 728,495  
Weighted Average Exercise Price $ 6.36 $ 6.27  
Weighted Average Remaining Contractual Life of Stock Options Vested 5 years 11 months 1 day 6 years 14 days  
Range 2 [Member]
      
Exercise price lower range limit $ 9 $ 9  
Exercise price upper range limit $ 12.90 $ 12.90  
Weighted Average Remaining Contractual Life - Years 4 years 8 months 12 days 4 years 11 months 8 days  
Number of options outstanding 130,037 130,037  
Weighted Average Exercise Price Stock Options Outstanding $ 10.46 $ 10.46  
Number of Awards Vested 130,037 130,037  
Weighted Average Exercise Price $ 10.46 $ 10.46  
Weighted Average Remaining Contractual Life of Stock Options Vested 4 years 8 months 12 days 4 years 11 months 8 days  
Range 3 [Member]
      
Exercise price lower range limit $ 13.50 $ 13.50  
Exercise price upper range limit $ 18.90 $ 18.90  
Weighted Average Remaining Contractual Life - Years 3 years 22 days 3 years 3 months 18 days  
Number of options outstanding 358,336 358,336  
Weighted Average Exercise Price Stock Options Outstanding $ 14.17 $ 14.17  
Number of Awards Vested 358,336 358,336  
Weighted Average Exercise Price $ 14.17 $ 14.17  
Weighted Average Remaining Contractual Life of Stock Options Vested 3 years 22 days 3 years 3 months 18 days  
Range 4 [Member]
      
Exercise price lower range limit $ 19.20 $ 19.20  
Exercise price upper range limit $ 23.85 $ 23.85  
Weighted Average Remaining Contractual Life - Years 2 years 4 months 24 days 2 years 7 months 24 days  
Number of options outstanding 306,668 306,668  
Weighted Average Exercise Price Stock Options Outstanding $ 22.84 $ 22.84  
Number of Awards Vested 306,668 306,668  
Weighted Average Exercise Price $ 22.84 $ 22.84  
Weighted Average Remaining Contractual Life of Stock Options Vested 2 years 4 months 24 days 2 years 7 months 24 days