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Earnings Per Share - Additional Information (Detail)
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3 Months Ended | 9 Months Ended | ||
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Sep. 30, 2013
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Sep. 30, 2012
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Sep. 30, 2013
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Sep. 30, 2012
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Common shares from potential exercise of certain stock options [Member]
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| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | ||||
| Antidilutive securities excluded from computation of earnings per share | 481,000 | 37,000 | 481,000 | 37,000 |
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Common shares from exercise of in-the-money options [Member]
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| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | ||||
| Antidilutive securities excluded from computation of earnings per share | 606,000 | 138,000 | 606,000 | |