Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Apr. 01, 2012	Mar. 31, 2013	Apr. 01, 2012	Sep. 30, 2012
Income Taxes [Line Items]
Effective income tax rate	425.80%	101.20%	88.10%	55.50%
Statutory rate	35.00%		35.00%
Valuation allowance, change in amount			$ 49.3
Unrecognized tax benefits	9.5		9.5		5.9
Uncertain tax positions [Member]
Income Taxes [Line Items]
Accrued interest and penalties related to the uncertain tax positions	3.8		3.8		3.6
Reinsurance transaction [Member]
Income Taxes [Line Items]
Valuation allowance, change in amount		(19.0)		(19.0)
Contingent purchase price reduction receivable [Member]
Income Taxes [Line Items]
Valuation allowance, change in amount		41.0		41.0
Business acquisition [Member]
Income Taxes [Line Items]
Valuation allowance, change in amount				(13.9)