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Long Term Incentive Plans - Additional Information (Detail) (USD $)
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1 Months Ended | 12 Months Ended | 1 Months Ended | ||||||||||||||
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Dec. 07, 2012
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Apr. 26, 2012
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May 01, 2012
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Dec. 31, 2012
Incentive Plans
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Dec. 31, 2011
Incentive Plans
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Dec. 31, 2010
Incentive Plans
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Feb. 13, 1997
Stock Options
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Apr. 28, 2011
Stock Options
Long Term Incentive Plan 2011
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Apr. 24, 2002
Stock Options
Long Term Incentive Plan 2002
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Feb. 13, 1997
Stock Options
Maximum
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Apr. 28, 2011
Stock Options
Maximum
Long Term Incentive Plan 2011
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Apr. 24, 2002
Stock Options
Maximum
Long Term Incentive Plan 2002
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Dec. 31, 2012
Non Performance Based
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Dec. 31, 2012
Performance Based
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||||||||||||||||
| Stock options authorized for grant | 1,000,000 | 500,000 | 500,000 | ||||||||||||||
| Stock options granted, term | 10 years | 10 years | 10 years | ||||||||||||||
| Stock options available for grant per individual employee | 400,000 | 200,000 | 200,000 | ||||||||||||||
| Available shares for future issuance | 560,000 | ||||||||||||||||
| Options exercised total intrinsic value | $ 250,000 | $ 133,000 | $ 58,000 | ||||||||||||||
| Proceeds from exercise of stock options | 17,000 | 167,000 | 101,000 | ||||||||||||||
| Excess tax benefit from share-based payment arrangements | 259,000 | 146,000 | 124,000 | ||||||||||||||
| Restricted stock vesting period minimum | 3 years | 1 year | |||||||||||||||
| Restricted stock granted annual increments beginning first anniversary of the date of grant | 20.00% | ||||||||||||||||
| Restricted stock granted | 57,250 | 1,000 | 2,000 | 60,250 | 67,600 | 52,100 | |||||||||||
| Restricted stock weighted average grant date fair value | $ 23.53 | $ 23.53 | $ 28.43 | $ 27.09 | |||||||||||||
| Total unrecognized compensation costs | 2,700,000 | ||||||||||||||||
| Recognition of compensation cost weighted average period | 3 years 9 months 18 days | ||||||||||||||||
| Total fair value of shares vested | 2,300,000 | ||||||||||||||||
| Compensation expense-stock compensation plans | 1,222,000 | 906,000 | 825,000 | 1,200,000 | 906,000 | 825,000 | |||||||||||
| Total income tax benefit under share-base compensation | $ 297,000 | $ 238,000 | $ 316,000 | ||||||||||||||