Share-Based Compensation - Summary of Stock Options Outstanding (Detail) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Sep. 30, 2016 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Stock options, beginning balance (shares) | shares	1,139
Stock options, exercised (shares) | shares	(632)
Stock options, forfeited, canceled or expired (shares) | shares	(12)
Stock options, ending balance (shares) | shares	495
Stock options, vested at ending balance (shares) | shares	490
Stock options, exercisable at ending balance (shares) | shares	452
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted average exercise price, beginning of period (USD per share) | $ / shares	$ 79.47
Weighted average exercise price, exercised (USD per share) | $ / shares	79.27
Weighted average exercise price, forfeited, canceled or expired (USD per share) | $ / shares	68.40
Weighted average exercise price, end of period (USD per share) | $ / shares	79.99
Stock options, weighted average exercise price, vested at ending balance (USD per share) | $ / shares	79.78
Stock options, weighted average exercise price, exercisable at ending balance (USD per share) | $ / shares	$ 77.72
Stock options, weighted average remaining contractual term, balance at ending balance	3 years 4 months 29 days
Stock options, weighted average remaining contractual term, vested at ending balance	3 years 4 months 22 days
Stock options, weighted average remaining contractual term, exercisable at ending balance	3 years 3 months 7 days
Stock options, aggregate intrinsic value, balance at ending balance | $	$ 49
Stock options, aggregate intrinsic value, vested at ending balance | $	49
Stock options, aggregate intrinsic value, exercisable at ending balance | $	$ 46