Stock Repurchase Program - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended
Nov. 30, 2011	Apr. 30, 2008	Sep. 30, 2012
Repurchase of authorized common stock	$ 80,000,000	$ 50,000,000
Repurchase of shares			1,375,875
Repurchase of shares, Value			$ 30,000,000

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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