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Changes in Non-Vested Stock Appreciation Awards (Detail) (Stock Appreciation Awards, USD $)
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12 Months Ended | ||
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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Stock Appreciation Awards
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Non-vested, beginning of period, Shares | 895,892 | 600,310 | 436,117 |
| Granted, Shares | 316,008 | 192,903 | |
| Vested, Shares | (867) | ||
| Forfeited, Shares | (61,147) | (20,426) | (27,483) |
| Expired, Shares | (390,174) | ||
| Non-vested, end of period, Shares | 444,571 | 895,892 | 600,310 |
| Non-vested, beginning of period, Weighted Average Grant Date Fair Value | $ 8.43 | $ 10.71 | $ 9.38 |
| Granted, Weighted Average Grant Date Fair Value | $ 4.02 | $ 13.81 | |
| Vested, Weighted Average Grant Date Fair Value | $ 12.64 | ||
| Forfeited, Weighted Average Grant Date Fair Value | $ 7.82 | $ 7.56 | $ 14.51 |
| Expired, Weighted Average Grant Date Fair Value | $ 9.38 | ||
| Non-vested, end of period, Weighted Average Grant Date Fair Value | $ 7.60 | $ 8.43 | $ 10.71 |