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Stock Plans - Additional Information (Detail)
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9 Months Ended |
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Sep. 30, 2012
Times
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Stock options expiration period |
10 years |
| Stock options exercisable period after grant date |
3 years |
| Restricted stock vest period after grant date |
3 years |
| Number of tranches in which restricted stock is vested |
3 |
| Restricted stock for management retention awards with various vesting periods, first tranche |
4 years |
| Restricted stock for management retention awards with various vesting periods, second tranche |
5 years |
| Restricted stock for management retention awards with various vesting periods, third tranche |
6 years |
| Performance period relative to a pre-determined peer group |
3 years |
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Minimum
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Percentage of target award based on achieving targeted performance conditions |
0.00% |
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Maximum
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Percentage of target award based on achieving targeted performance conditions |
200.00% |