Share-Based Compensation Plans - Summary of Company's Share Awards (Detail) (USD $)	3 Months Ended	6 Months Ended
	Mar. 31, 2014	Mar. 31, 2014 Deferred Equity Units	Mar. 31, 2014 Matching Equity Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested units at September 30, 2013		24	24
Units, Granted		2	2
Units, Vested		(5)
Units, Forfeited		(1)	(1)
Unvested units at March 31, 2014		20	25
Unvested units, Weighted Average Fair Value at September 30, 2013		$ 134.62
Weighted-Average Fair Value, Granted		$ 134.62
Weighted-Average Fair Value, Vested		$ 134.62
Weighted-Average Fair Value, Forfeited		$ 134.62
Unvested units, Weighted average Fair Value at March 31, 2014		$ 134.62
Unvested units, Weighted-Average Intrinsic Value at September 30, 2013			$ 27.49
Weighted-Average Intrinsic Value, Granted	$ 107.13
Weighted-Average Intrinsic Value, Vested			$ 27.49
Weighted-Average Intrinsic Value, Forfeited			$ 27.49
Unvested units, Weighted-Average Intrinsic Value at March 31, 2014			$ 25.20
Unvested units, Weighted-Average Grant-Date Intrinsic Value at September 30, 2013		$ 107.13
Weighted-Average Grant-Date Intrinsic Value, Granted		$ 107.13
Weighted-Average Grant-Date Intrinsic Value, Vested		$ 107.13
Weighted-Average Grant-Date Intrinsic Value, Forfeited		$ 107.13
Unvested units, Weighted-Average Grant-Date Intrinsic Value at March 31, 2014		$ 107.13