v3.3.0.814
Stockholders' Equity Effect of Escrow Funding on the Company Repurchaseing its Common Stock (Details)
$ / shares in Units, shares in Millions, $ in Millions
 12 Months Ended
Sep. 30, 2015
conversion_rate
shares
Sep. 30, 2015
USD ($)
conversion_rate
Sep. 30, 2014
USD ($)
$ / shares
shares
Mar. 19, 2015
conversion_rate
Class of Stock [Line Items]        
As-converted class B common stock outstanding after deposits [1] 2,434      
Deposit into Litigation Escrow        
Class of Stock [Line Items]        
Deposits under the retrospective responsibility plan | $   $ 0 $ 450  
Weighted-average repurchase price per share | $ / shares [2]     $ 53.83  
Class A common stock        
Class of Stock [Line Items]        
As-converted class B common stock outstanding after deposits [1] 1,950      
Class A common stock | Deposit into Litigation Escrow        
Class of Stock [Line Items]        
Equivalent shares of class A common stock repurchased     8  
Class B common stock        
Class of Stock [Line Items]        
Common stock, conversion rate | conversion_rate [3] 1.6483 1.6483   1.6483
As-converted class B common stock outstanding after deposits [1] 405      
Class B common stock | Deposit into Litigation Escrow        
Class of Stock [Line Items]        
Common stock, conversion rate     1.6483  
As-converted class B common stock outstanding after deposits     405  
[1] Figures in the table may not recalculate exactly due to rounding. As-converted class A common stock is calculated based on unrounded numbers.
[2] Effective price per share calculated using the volume-weighted average price of the Company's class A common stock over a pricing period in accordance with the Company's current certificate of incorporation.
[3] 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.