Stock-Based Compensation (Summary of Weighted-Average Grant-Date Fair Value and Intrinsic Value of Restricted Units Vested) (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	6 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant-date fair value per share	$ 15.26	$ 22.32
Total intrinsic value of shares vested (in millions)	$ 70.2	$ 117.6
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant-date fair value per share	$ 15.71