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Property and Equipment - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Property Plant And Equipment [Abstract]        
Depreciation expense $ 7.0 $ 7.9 $ 13.7 $ 14.7