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Schedule of Disclosure of Share-based Compensation Arrangements by Share-based Payment Award (Details) (USD $)
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6 Months Ended | 12 Months Ended | 6 Months Ended | 12 Months Ended | 6 Months Ended | 12 Months Ended | 6 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|---|---|---|---|---|---|
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Jun. 30, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Jun. 30, 2012
Range 1 [Member]
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Dec. 31, 2011
Range 1 [Member]
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Jun. 30, 2012
Range 2 [Member]
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Dec. 31, 2011
Range 2 [Member]
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Jun. 30, 2012
Range 3 [Member]
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Dec. 31, 2011
Range 3 [Member]
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Jun. 30, 2012
Range 4 [Member]
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Dec. 31, 2011
Range 4 [Member]
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| Exercise price lower range limit | $ 4.5 | $ 4.5 | $ 9 | $ 9 | $ 13.5 | $ 13.5 | $ 19.2 | $ 19.2 | |||
| Exercise price upper range limit | $ 8.7 | $ 8.7 | $ 12.9 | $ 12.9 | $ 18.9 | $ 18.9 | $ 23.85 | $ 23.85 | |||
| Weighted Average Remaining Contractual Life - Years | 5 years 6 months | 5 years 8 months 8 days | 6 years 9 months 25 days | 7 years 25 days | 5 years 8 months 1 day | 5 years 29 days | 4 years 11 days | 4 years 3 months 4 days | 3 years 4 months 24 days | 3 years 7 months 24 days | |
| Number of options outstanding | 1,668,898 | 1,674,065 | 1,772,348 | 871,028 | 871,195 | 130,673 | 152,340 | 360,529 | 343,862 | 306,668 | 306,668 |
| Number of Awards Vested | 1,478,768 | 1,345,541 | 680,898 | 542,671 | 130,673 | 152,340 | 360,529 | 343,862 | 306,668 | 306,668 | |
| Weighted Average Exercise Price | $ 12.05 | $ 12.62 | $ 6.37 | $ 6.48 | $ 10.45 | $ 10.51 | $ 14.17 | $ 14.14 | $ 22.84 | $ 22.84 |