Quarterly report pursuant to Section 13 or 15(d)

Income Taxes - Additional Information (Detail)

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Income Taxes - Additional Information (Detail) (USD $)
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Income Tax Disclosure [Abstract]              
Income taxes $ 45,464,000 $ 45,424,000 $ 133,775,000 $ 141,811,000 $ 186,944,000 $ 144,820,000 $ 87,212,000
Effective income tax rate 24.30% 28.90% 24.90% 28.70%      
Total amount of unrecognized tax benefits, including related interest and penalties 33,100,000   33,100,000        
Unrecognized tax benefits excluding interest and penalties that if recognized would affect the effective tax rate 26,300,000   26,300,000        
Total accrued interest for tax contingencies 3,400,000   3,400,000        
Total accrued penalties for tax contingencies 800,000   800,000        
Amount of unrecognized tax benefits that could decrease within the next 12 months 9,800,000   9,800,000        
Decrease in unrecognized tax benefits due to the settlement of audits or resolution of administrative or judicial proceedings 6,800,000   6,800,000        
Decrease in unrecognized tax benefits expiration of statute of limitations $ 3,000,000   $ 3,000,000