Share-based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Jan. 26, 2021	Jan. 25, 2021
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period of options issued under EIP	10 years
Vesting period from the date of grant	3 years
Total intrinsic value from options exercised	$ 56	$ 124	$ 146
Tax benefit from exercise of stock options	11	$ 23	$ 31
Unrecognized compensation cost	$ 22
Total unrecognized compensation cost related to non-vested options expected to be recognized over a weighted average period (in years)	4 months 17 days
Risk-free rate of return	1.10%	0.30%	1.60%
Expected term (in years)	4 years 1 month 9 days	4 years 25 days	4 years 10 days
Expected volatility	27.10%	25.10%	18.70%
Expected dividend yield	0.70%	0.60%	0.70%
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period from the date of grant	3 years
Unrecognized compensation cost	$ 692
Weighted average grant date fair value (in dollars per share)	$ 204.73	$ 209.00	$ 183.61
Total grant date fair value of shares vested and earned	$ 380	$ 331	$ 284
Weighted-average period	1 year 25 days
Performance-based Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period from the date of grant	3 years
Unrecognized compensation cost	$ 39
Weighted average grant date fair value (in dollars per share)	$ 186.50
Total grant date fair value of shares vested and earned	$ 49	$ 47	$ 65
Weighted-average period	10 months 20 days
Risk-free rate of return	0.50%	0.20%	1.60%
Expected term (in years)	2 years 18 days	2 years	1 year 10 months 24 days
Expected volatility	28.30%	27.20%	20.90%
Expected dividend yield	0.80%	0.60%	0.70%
2007 Equity Incentive Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of Class A Common Stock authorized for issuance under EIP or ESPP (in shares)				198	236
Share-based compensation expense under EIP	$ 571	$ 518	$ 393
Tax benefit under EIP	$ 82	$ 73	$ 63
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of Class A Common Stock authorized for issuance under EIP or ESPP (in shares)	20
ESPP discount from market price	15.00%