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Pension Plans and Other Postretirement Benefits - Additional Information (Detail) (USD $)
3 Months Ended 6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Compensation And Retirement Disclosure [Abstract]        
Defined contribution pension and retirement savings plans total expense $ 12,563,000 $ 11,390,000 $ 28,318,000 $ 26,015,000