Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012	Sep. 30, 2012
Income Tax Disclosure [Line Items]
Income tax provisions associated with income from continuing operations	$ 0.9	$ 1.2	$ 2.8	$ 2.5
Effective tax rates	21.20%	39.00%	26.70%	37.50%
Permanent tax and discrete tax benefits	0.4		0.6
U.S. federal statutory tax rate	35.00%	35.00%	35.00%	35.00%
Income tax expense from discontinued operations	0.3	0.1	0.3	1.0
Income tax benefit from the sale of discontinued operations		0.1		0.7
Effective tax rate applied to discontinued operations	32.80%	14.40%	32.80%	51.40%
Unrecognized tax benefits including interest and penalties	1.4		1.4		1.4
Liability for unrecognized tax benefits to change significantly in the next 12 months	$ 0		$ 0