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 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Operating Leased Assets [Line Items]        
Operating lease expense $ 6.2 $ 7.9 $ 12.5 $ 13.7