v3.21.2
Income Taxes - Additional Information (Detail) - USD ($)
 12 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2016
Sep. 30, 2018
Tax Credit Carryforward [Line Items]          
US income before taxes $ 11,002,000,000 $ 9,178,000,000 $ 9,536,000,000    
Non-recurring, non-cash tax expense related to the remeasurement of UK deferred tax liabilities 1,000,000,000 329,000,000   $ 1,000,000,000  
Deferred tax assets, net $ 1,046,000,000 $ 846,000,000      
Effective income tax rate 23.00% 21.00% 19.00%    
Recognized tax benefit $ 255,000,000 $ 0 $ 0    
Income taxes receivable included in prepaid and other current assets 83,000,000 93,000,000      
Income taxes payable included in accrued taxes as part of accrued liabilities 325,000,000 134,000,000      
Accrued income taxes included in other long-term liabilities 2,400,000,000 2,800,000,000      
Decreased Singapore tax as a result of the tax incentive agreement $ 273,000,000 $ 280,000,000 $ 324,000,000    
Benefit of the tax incentive agreement on diluted net income per share (in dollars per share) $ 0.12 $ 0.13 $ 0.14    
Total unrecognized tax benefits exclusive of interest and penalties $ 2,488,000,000 $ 2,579,000,000 $ 2,234,000,000   $ 1,658,000,000
Unrecognized tax benefits, if recognized, would reduce the effective tax rate in a future period 1,300,000,000 1,600,000,000 1,400,000,000    
Interest expense included in interest expense and administrative and other 1,000,000 68,000,000 66,000,000    
Accrued penalties related to uncertain tax positions 3,000,000 4,000,000 5,000,000    
Accrued interest related to uncertain tax positions in other long term liabilities 233,000,000 233,000,000      
Accrued penalties related to uncertain tax positions in other long term liabilities 34,000,000 31,000,000      
Domestic Tax Authority          
Tax Credit Carryforward [Line Items]          
Net operating loss carryforwards 42,000,000        
State and Local Jurisdiction          
Tax Credit Carryforward [Line Items]          
Net operating loss carryforwards 15,000,000        
Foreign Country          
Tax Credit Carryforward [Line Items]          
Net operating loss carryforwards 390,000,000        
Other Assets          
Tax Credit Carryforward [Line Items]          
Deferred tax assets, net 80,000,000 63,000,000      
Non-current income tax receivable 974,000,000 988,000,000      
Non United States Customers          
Tax Credit Carryforward [Line Items]          
US income before taxes $ 3,100,000,000 $ 3,000,000,000 $ 3,000,000,000