Quarterly report pursuant to Section 13 or 15(d)

Lease Obligations (Narrative) (Detail)

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Lease Obligations (Narrative) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Leases [Abstract]        
Operating lease expense $ 6.7 $ 4.2 $ 19.2 $ 17.9