Plan Assets Investment Policy Ranges for Major Asset Classes (Detail)	12 Months Ended
	Sep. 29, 2012
Equity investments
Defined Benefit Plan Disclosure [Line Items]
Asset allocation range, minimum	31.00%
Asset allocation range, maximum	60.00%
Equity investments | U S Small Cap
Defined Benefit Plan Disclosure [Line Items]
Asset allocation range, minimum	0.00%
Asset allocation range, maximum	10.00%
Equity investments | US Mid / Large cap
Defined Benefit Plan Disclosure [Line Items]
Asset allocation range, minimum	15.00%
Asset allocation range, maximum	30.00%
Equity investments | International
Defined Benefit Plan Disclosure [Line Items]
Asset allocation range, minimum	7.00%
Asset allocation range, maximum	37.00%
Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Asset allocation range, minimum	20.00%
Asset allocation range, maximum	40.00%
Alternative Investments
Defined Benefit Plan Disclosure [Line Items]
Asset allocation range, minimum	15.00%
Asset allocation range, maximum	30.00%
Alternative Investments | Diversified
Defined Benefit Plan Disclosure [Line Items]
Asset allocation range, minimum	0.00%
Asset allocation range, maximum	10.00%
Alternative Investments | Distressed
Defined Benefit Plan Disclosure [Line Items]
Asset allocation range, minimum	0.00%
Asset allocation range, maximum	10.00%
Alternative Investments | Private Equity/Venture capital
Defined Benefit Plan Disclosure [Line Items]
Asset allocation range, minimum	0.00%
Asset allocation range, maximum	12.00%
Alternative Investments | Real estate
Defined Benefit Plan Disclosure [Line Items]
Asset allocation range, minimum	0.00%
Asset allocation range, maximum	15.00%
Alternative Investments | Commodities Investment
Defined Benefit Plan Disclosure [Line Items]
Asset allocation range, minimum	0.00%
Asset allocation range, maximum	10.00%
Cash
Defined Benefit Plan Disclosure [Line Items]
Asset allocation range, minimum	0.00%
Asset allocation range, maximum	10.00%