v3.3.0.814
Debt - Additional Information (Detail) - USD ($)
12 Months Ended
Sep. 30, 2015
Sep. 30, 2014
Revolving Credit Facility    
Debt Instrument [Line Items]    
Credit Facility Maximum Borrowing Capacity $ 3,000,000,000 $ 3,000,000,000
Credit Facility Commitment Fee Percentage 0.07%  
Credit Facility Amount Outanding $ 0  
Revolving Credit Facility | Minimum    
Debt Instrument [Line Items]    
Credit Facility Interest Rate During Period 0.00%  
Revolving Credit Facility | Maximum    
Debt Instrument [Line Items]    
Credit Facility Interest Rate During Period 0.75%  
Commercial Paper    
Debt Instrument [Line Items]    
Commercial Paper Program, Amount Available $ 3,000,000,000  
Commercial Paper Program, Maturity Period P397D  
Commercial Paper Program, Amount Outstanding $ 0