Earnings Per Share - Summary of Basic and Diluted EPS (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Preferred Stock Dividends, Income Statement Impact		$ (19.2)
Preferred Stock, Accretion of Redemption Discount		(12.1)
Preferred Stock Conversions, Inducements		68.9
Dilutive Adjustments To Income Loss Attributable To Common Stock From Assumed Conversion Of Preferred Stock Net Of Tax		(37.6)
Net income (loss) attributable to common and participating preferred stockholders	(39.0)	62.0
Participating shares at end of period:
Common shares outstanding	139,574	139,724
Preferred shares (as-converted basis)	61,986	62,839
Total	201,560	202,563
Percentage of income (loss) allocated to:
Common shares	100.00%	69.00%
Preferred shares (a)	0.00%	31.00%
Net income (loss) attributable to common shares - basic	(39.0)	42.8
Dilutive adjustments to income (loss) attributable to common shares from assumed conversion of preferred shares, net of tax:
Net income (loss) attributable to common shares - diluted	$ (39.0)	$ 5.2
Weighted-average common shares outstanding - basic	139,173	139,483
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Preferred Stock		62,839
Dilutive effect of unvested restricted stock and restricted stock units		1,089
Dilutive effect of stock options		786
Weighted-average shares outstanding - diluted	139,173	204,197
Net (loss) income per common share attributable to controlling interest:
Basic (in dollars per share)	$ (0.28)	$ 0.31
Diluted (in dollars per share)	$ (0.28)	$ 0.03