Share-Based Compensation - Summary of Stock Options Outstanding (Detail) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Sep. 30, 2015 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Stock options, beginning balance (shares)	74
Stock options granted during the period, acquisition-related conversion (shares)	1,971
Stock options, exercised (shares)	(900)
Stock options, forfeited, canceled or expired (shares)	(7)
Stock options, ending balance (shares)	1,139
Stock options, vested at ending balance (shares)	1,111
Stock options, exercisable at ending balance (shares)	865
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	$ 54.57
Weighted average exercise price, granted, acquisition-related conversation (USD per share) | $ / shares	82.32
Weighted average exercise price, exercised (USD per share) | $ / shares	83.70
Weighted average exercise price, forfeited, canceled or expired (USD per share) | $ / shares	73.41
Weighted average exercise price, end of period (USD per share) | $ / shares	79.47
Stock options, weighted average exercise price, vested at ending balance (USD per share) | $ / shares	79.10
Stock options, weighted average exercise price, exercisable at ending balance (USD per share) | $ / shares	$ 74.82
Stock options, weighted average remaining contractual term, balance at ending balance	4 years 3 months 22 days
Stock options, weighted average remaining contractual term, vested at ending balance	4 years 3 months 15 days
Stock options, weighted average remaining contractual term, exercisable at ending balance	3 years 11 months 27 days
Stock options, aggregate intrinsic value, balance at ending balance | $	$ 61
Stock options, aggregate intrinsic value, vested at ending balance | $	60
Stock options, aggregate intrinsic value, exercisable at ending balance | $	$ 50