Change in Accounting Principle and Change in Accounting Estimate - Additional Information (Detail) (USD $)
3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2012
Sep. 30, 2011
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Costs related to acquisition $ 8,800,000 $ 27,800,000  
Net result of adoption of new accounting policy 500,000 2,000,000  
Depreciation as an operating expense 3,700,000 6,105,000 2,345,000
Previous Accounting Guidance
     
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Costs related to acquisition 8,200,000 25,700,000  
Impact of Change in Accounting Principle
     
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Costs related to acquisition $ 600,000 $ 2,100,000