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Stock Buy Back Plans - Number of Shares Purchased and Maximum Value of Shares That yet be Purchased Under Plan (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2013
Equity [Abstract]          
Total Number of Shares Purchased 351,313       26,593 377,906
Average Price Paid Per Share $ 36.69       $ 33.94 $ 36.49
Total Number of Shares Purchased as Part of Publicly Announced Plan 351,313       26,593 377,906
Maximum Value of Shares that May Yet Be Purchased Under the Plan    $ 12,888 $ 12,888 $ 12,888