Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

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Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
Share data in Millions, unless otherwise specified
 3 Months Ended 6 Months Ended
Jun. 30, 2011
Jun. 30, 2011
Jun. 30, 2012
Dec. 31, 2011
Significant Accounting Policies [Line Items]        
Antidilutive stock options excluded from computation of earnings per share 1.3 1.4    
Fair value of long term debt     $ 1,100,000,000 $ 1,090,000,000
Carrying value of long term debt     970,000,000 970,000,000
Variable interest maximum exposure to loss     11,400,000  
Fair Value, Measurements, Recurring
        
Significant Accounting Policies [Line Items]        
Fair value of interest rate swaps     $ 14,000,000 [1] $ 14,800,000
Interest rate swap term     5 years 5 years
[1] The fair value of our interest rate swaps, which are designated as fair value hedges, and notes, due in 2014 are based on the present value of expected future cash flows using zero coupon rates and are classified within Level 2 of the fair value hierarchy.