Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity (Details Textual)

v3.8.0.1
Stockholders' Equity (Details Textual)
1 Months Ended 2 Months Ended 12 Months Ended
Apr. 23, 2018
USD ($)
shares
Mar. 31, 2018
$ / shares
Apr. 23, 2018
USD ($)
shares
Feb. 28, 2018
USD ($)
class_of_stock
$ / shares
shares
Feb. 28, 2017
USD ($)
$ / shares
Feb. 29, 2016
USD ($)
$ / shares
Jan. 31, 2018
USD ($)
Nov. 30, 2016
USD ($)
Apr. 30, 2012
USD ($)
Class of Stock [Line Items]                  
Number of classes of common stock with a material number of shares outstanding | class_of_stock       2          
Dollar value of shares repurchased       $ 1,038,500,000 $ 1,122,700,000 $ 33,800,000      
Class B Convertible Common Stock [Member]                  
Class of Stock [Line Items]                  
Common stock, conversion features       convertible into shares of Class A Common Stock on a one-to-one basis          
Common stock, voting rights       ten votes per share          
Cash dividends declared per common share | $ / shares       $ 1.88 $ 1.44 $ 1.12      
Class B Convertible Common Stock [Member] | Subsequent Event [Member]                  
Class of Stock [Line Items]                  
Cash dividends declared per common share | $ / shares   $ 0.67              
Class A Common Stock [Member]                  
Class of Stock [Line Items]                  
Common stock, voting rights       one vote per share          
Common stock, dividend rights       10.00%          
Cash dividends declared per common share | $ / shares       $ 2.08 $ 1.60 $ 1.24      
Class A Common Stock [Member] | Subsequent Event [Member]                  
Class of Stock [Line Items]                  
Cash dividends declared per common share | $ / shares   0.74              
Class A Common Stock [Member] | 2013 Authorization [Member] | Subsequent Event [Member]                  
Class of Stock [Line Items]                  
Share repurchases | shares 18,670,632                
Dollar value of shares repurchased $ 1,000,000,000                
Class A Common Stock [Member] | 2017 Authorization [Member]                  
Class of Stock [Line Items]                  
Share repurchases | shares       2,530,194          
Dollar value of shares repurchased       $ 546,900,000          
Class A Common Stock [Member] | 2017 Authorization [Member] | Subsequent Event [Member]                  
Class of Stock [Line Items]                  
Share repurchases | shares 5,536,741                
Dollar value of shares repurchased $ 1,000,000,000                
Class A Common Stock [Member] | 2018 Authorization [Member]                  
Class of Stock [Line Items]                  
Share repurchases | shares       2,279,867          
Dollar value of shares repurchased       $ 491,600,000          
Class A Common Stock [Member] | 2018 Authorization [Member] | Subsequent Event [Member]                  
Class of Stock [Line Items]                  
Share repurchases | shares 2,373,154   93,287            
Dollar value of shares repurchased $ 512,800,000   $ 21,200,000            
Class 1 Common Stock [Member]                  
Class of Stock [Line Items]                  
Common stock, conversion features       convertible into shares of Class A Common Stock on a one-to-one basis          
Common stock, voting rights       generally have no voting rights          
Class 1 Common Stock [Member] | Subsequent Event [Member]                  
Class of Stock [Line Items]                  
Cash dividends declared per common share | $ / shares   $ 0.67              
Class A and Class B [Member] | 2013 Authorization [Member]                  
Class of Stock [Line Items]                  
Maximum authorized repurchase of common stock                 $ 1,000,000,000.0
Class A and Class B [Member] | 2017 Authorization [Member]                  
Class of Stock [Line Items]                  
Maximum authorized repurchase of common stock               $ 1,000,000,000  
Class A and Class B [Member] | 2018 Authorization [Member]                  
Class of Stock [Line Items]                  
Maximum authorized repurchase of common stock             $ 3,000,000,000.0