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Employee Benefit Plans - Summary of Options and SARs Under Share-based Compensation Plan (Detail) (USD $)
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12 Months Ended |
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Dec. 31, 2013
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| Share Based Compensation Arrangements By Share Based Payment Award Options [Line Items] |
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| Options outstanding at beginning of year, Number of Shares |
897,450 |
| Options granted, Number of Shares |
49,700 |
| Options exercised, Number of Shares |
(3,700) |
| Options outstanding at end of year, Number of Shares |
933,450 |
| Options exercisable at end of year, Number of Shares |
763,540 |
| Options outstanding at beginning of year, Weighted-Average Exercise Price |
$ 9.58 |
| Options granted, Weighted-Average Exercise Price |
$ 18.52 |
| Options exercised, Weighted-Average Exercise Price |
$ 9.47 |
| Options outstanding at end of year, Weighted-Average Exercise Price |
$ 10.06 |
| Options exercisable at end of year, Weighted-Average Exercise Price |
$ 9.42 |
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Stock Appreciation Rights (SARs) [Member]
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| Share Based Compensation Arrangements By Share Based Payment Award Options [Line Items] |
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| Options exercised, Number of Shares |
(10,000) |
| Options exercised, Weighted-Average Exercise Price |
$ 9.43 |