v3.3.0.814
Stockholders' Equity - Additional Information (Detail)
$ / shares in Units, $ in Millions
12 Months Ended
Mar. 19, 2015
conversion_rate
Sep. 30, 2015
USD ($)
conversion_rate
$ / shares
shares
Sep. 30, 2014
USD ($)
shares
Oct. 31, 2015
USD ($)
$ / shares
Oct. 31, 2014
USD ($)
Class of Stock [Line Items]          
Share repurchase plan, authorized amount         $ 5,000
Stock repurchase plan, remaining authorized funds   $ 2,800      
Dividends, paid   $ 1,200      
Dividends, paid per share | $ / shares   $ 0.12      
Subsequent Event          
Class of Stock [Line Items]          
Share repurchase plan, authorized amount       $ 5,000  
Dividends, per share amount declared | $ / shares       $ 0.14  
Deposit into Litigation Escrow          
Class of Stock [Line Items]          
Deposits into litigation escrow account   $ 0 $ 450    
Class A common stock          
Class of Stock [Line Items]          
Common stock split, conversion ratio 4        
Class B common stock          
Class of Stock [Line Items]          
Common stock, conversion rate | conversion_rate [1] 1.6483 1.6483      
Class B common stock | Deposit into Litigation Escrow          
Class of Stock [Line Items]          
Common stock, conversion rate     1.6483    
Class C common stock          
Class of Stock [Line Items]          
Common stock, conversion rate | conversion_rate 4.0 4.0      
Class C common stock | Accelerated Share Repurchase Program Aggregate          
Class of Stock [Line Items]          
Shares of class C common stock released from transfer restrictions, converted to class A common stock | shares   132,000,000      
Preferred stock          
Class of Stock [Line Items]          
Preferred stock, shares outstanding | shares   0 0    
[1] The class B to class A common stock conversion rate is presented on a rounded basis. Conversion calculations for dividend payments are based on a conversion rate rounded to the tenth decimal.