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Stock-Based Compensation - Summary of Stock Option Activity (Detail) (USD $)
9 Months Ended
Sep. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]  
Number of Shares, Beginning Balance 220,349
Number of Shares, Exercised (25,512)
Number of Shares, Forfeited (363)
Number of Shares, Ending Balance 194,474
Weighted Average Exercise Price, Beginning Balance $ 20.03
Weighted Average Exercise Price, Exercised $ 18.76
Weighted Average Exercise Price, Forfeited $ 55.18
Weighted Average Exercise Price, Ending Balance $ 20.13