Investments - Schedule of Allowance for Credit Losses (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
Allowance for credit losses:
Balance at beginning of period	$ 2.6		$ 1.4
Provision for credit losses	0.2	0.2	1.4	0.2
Charge-offs
Recoveries
Balance at end of period	$ 2.8	$ 0.2	$ 2.8	$ 0.2