v2.4.0.6
Stockholders' Equity (Details) (USD $)
In Millions, except Per Share data, unless otherwise specified
1 Months Ended 12 Months Ended
Nov. 30, 2010
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Stockholders Equity (Textual) [Abstract]        
Maximum amount authorized to repurchase common stock by Board of Director $ 400.0 $ 750.0    
Purchase of common stock, shares   17.1    
Amount used to repurchase of common stock   500.8    
Average cost per share of common stock   $ 29.21    
Quarterly dividend per share   $ 0.22    
Cash dividends declared   314.1 298.8 288.7
Quarterly dividend payable   $ 81.4 $ 76.7