Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity (Details 1)

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Stockholders' Equity (Details 1) - USD ($)
 2 Months Ended 12 Months Ended
Apr. 23, 2018
Apr. 23, 2018
Feb. 28, 2018
Feb. 28, 2017
Feb. 29, 2016
Jan. 31, 2018
Nov. 30, 2016
Apr. 30, 2012
Equity, Class of Treasury Stock [Line Items]                
Dollar Value of Shares Repurchased     $ 1,038,500,000 $ 1,122,700,000 $ 33,800,000      
Class A and Class B [Member] | 2013 Authorization [Member]                
Equity, Class of Treasury Stock [Line Items]                
Repurchase Authorization               $ 1,000,000,000.0
Class A and Class B [Member] | 2017 Authorization [Member]                
Equity, Class of Treasury Stock [Line Items]                
Repurchase Authorization             $ 1,000,000,000  
Class A and Class B [Member] | 2018 Authorization [Member]                
Equity, Class of Treasury Stock [Line Items]                
Repurchase Authorization           $ 3,000,000,000.0    
Class A Common Stock [Member] | 2013 Authorization [Member] | Subsequent Event [Member]                
Equity, Class of Treasury Stock [Line Items]                
Dollar Value of Shares Repurchased $ 1,000,000,000              
Number of Shares Repurchased 18,670,632              
Class A Common Stock [Member] | 2017 Authorization [Member]                
Equity, Class of Treasury Stock [Line Items]                
Dollar Value of Shares Repurchased     $ 546,900,000          
Number of Shares Repurchased     2,530,194          
Class A Common Stock [Member] | 2017 Authorization [Member] | Subsequent Event [Member]                
Equity, Class of Treasury Stock [Line Items]                
Dollar Value of Shares Repurchased $ 1,000,000,000              
Number of Shares Repurchased 5,536,741              
Class A Common Stock [Member] | 2018 Authorization [Member]                
Equity, Class of Treasury Stock [Line Items]                
Dollar Value of Shares Repurchased     $ 491,600,000          
Number of Shares Repurchased     2,279,867          
Class A Common Stock [Member] | 2018 Authorization [Member] | Subsequent Event [Member]                
Equity, Class of Treasury Stock [Line Items]                
Dollar Value of Shares Repurchased $ 512,800,000 $ 21,200,000            
Number of Shares Repurchased 2,373,154 93,287