Share-based Compensation - Additional Information (Detail) $ / shares in Units, shares in Millions, $ in Millions		12 Months Ended
	Mar. 19, 2015	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) $ / shares	Sep. 30, 2014 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of Class A Common Stock authorized for issuance under the 2007 Equity Incentive Compensation Plan ("the "EIP") | shares		20
Share-based compensation expense		$ 211	$ 184	$ 172
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		$ 62	54	51
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period		10 years
Total intrinsic value from options exercised		$ 103	134	187
Tax benefit realized from options exercised		35	86	65
Unrecognized compensation cost		$ 19
Total unrecognized compensation cost related to non-vested options expected to be recognized over a weighted average period (in years)		1 year 4 months 24 days
Total fair value of RSAs and RSUs vested		$ 142	$ 132	$ 126
Weighted average remaining contractual term		5 years 2 months 19 days
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date		15.00%
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period from the date of grant		3 years
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost		$ 54
Weighted average grant date fair value (in dollars per share) | $ / shares		$ 0.00	$ 63.71	$ 49.98
Weighted average remaining contractual term		10 months 6 days
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost		$ 140
Weighted average grant date fair value (in dollars per share) | $ / shares		$ 79.77	$ 62.88	$ 49.44
Weighted average remaining contractual term		1 year 7 months 27 days
Performance Based Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period from the date of grant		3 years	3 years	3 years
Unrecognized compensation cost		$ 18
Weighted average grant date fair value per share | $ / shares		$ 92.71	$ 69.78	$ 56.37
Class A common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock split, conversion ratio	4
Equity Incentive Compensation Plan, 2007 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of Class A Common Stock authorized for issuance under the 2007 Equity Incentive Compensation Plan ("the "EIP") | shares		236