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Property and Equipment - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
1 Months Ended 12 Months Ended 263 Months Ended
Dec. 31, 2009
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2012
Property, Plant and Equipment [Line Items]          
Amortization period of leasehold improvements   4 years      
Depreciation and amortization expense   $ 13.0 $ 14.6 $ 16.5 $ 121.8
Loss on disposal of asset $ (12.8)