Annual report pursuant to Section 13 and 15(d)

Capital Structure and Per Share Data - Additional Information (Detail)

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Capital Structure and Per Share Data - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
 12 Months Ended
Dec. 31, 2013
Vote
Dec. 31, 2012
Dec. 31, 2011
Capital Structure and Per Share Data [Line Items]      
Preferred stock shares authorized 3,000,000    
Preferred stock, issued 0 0  
Preferred stock, outstanding 0 0  
Number of classes of common stock 2    
Stated interest rate on debt agreement   5.00% 5.00%
5.0% Convertible Senior Notes [Member]
      
Capital Structure and Per Share Data [Line Items]      
Stated interest rate on debt agreement 5.00% 5.00% 5.00%
Class A Convertible Preferred Stock [Member]
      
Capital Structure and Per Share Data [Line Items]      
Preferred stock shares authorized 300,000    
Preferred stock par value $ 0.10    
Class A convertible preferred stock shares redeemed 13,802    
Class A convertible preferred stock redemption price $ 1,000    
Series I Preferred Stock [Member]
      
Capital Structure and Per Share Data [Line Items]      
Class A Convertible Preferred Stock Shares Authorized 100,000    
Series II Preferred Stock [Member]
      
Capital Structure and Per Share Data [Line Items]      
Class A Convertible Preferred Stock Shares Authorized 100,000    
Series III Preferred Stock [Member]
      
Capital Structure and Per Share Data [Line Items]      
Class A Convertible Preferred Stock Shares Authorized 100,000    
Common Class A [Member]
      
Capital Structure and Per Share Data [Line Items]      
Common stock, shares authorized 100,000,000 100,000,000  
Common stock, par value $ 0.01 $ 0.01  
Common stock, number of votes per share 1    
Number of shares of class A common stock issuable against each share of class B common stock 1    
Authorized amount expend on repurchase of shares $ 495.0    
Common stock class A, shares repurchased 20,900,000    
Common stock class A, share repurchase price per share $ 16.68    
Remaining authorized amount $ 132.5    
Antidilutive stock options excluded in computation of diluted earnings per share 800,000 1,000,000 1,900,000
Common Class B [Member]
      
Capital Structure and Per Share Data [Line Items]      
Common stock, shares authorized 30,000,000 30,000,000  
Common stock, par value $ 0.01 $ 0.01  
Common stock, number of votes per share 10