v3.6.0.2
Common and Preferred Shares and Warrants (Details Textuals) - USD ($)
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Sep. 26, 2016
Common And Preferred Shares And Warrants (Textuals) [Abstract]        
Common share repurchases authorized       150,000,000
Common shares repurchased 70,000,000 58,800,000 49,000,000  
Cost basis of common stock repurchased $ 4,431,000,000 $ 4,480,000,000 $ 4,389,000,000  
Commissions paid included in cost basis of common stock repurchased $ 1,200,000 $ 1,100,000 $ 1,000,000  
Common shares remaining under share repurchase authorizations 135,000,000      
Shares held as treasury shares 3,000,000 3,000,000 3,200,000  
Cost basis of treasury stock $ 197,000,000 $ 242,000,000 $ 280,000,000  
Preferred shares, authorized 20,000,000 20,000,000    
Preferred shares, par value $ 1.67 $ 1.67    
Depositary Shares, Redemption Amount $ 1,000      
Warrants, issued and outstanding 0 0 0  
Liquidation price per share $ 1,000,000