Debt - Additional Information (Detail) (USD $)					6 Months Ended		9 Months Ended
	Sep. 30, 2012	Aug. 24, 2012	Feb. 29, 2012	Aug. 26, 2011	Aug. 24, 2012 Credit Agreement [Member]	Aug. 24, 2012 Accounts Receivable Facility [Member]	Sep. 30, 2012 Amended And Restated Receivables Purchase Agreement [Member]	Sep. 21, 2012 Amended And Restated Receivables Purchase Agreement [Member]	Aug. 24, 2012 Publicly Traded [Member]	Feb. 29, 2012 Publicly Traded [Member]	Aug. 26, 2011 Publicly Traded [Member]	Aug. 24, 2012 Non Publicly Traded [Member]
Debt Instrument [Line Items]
Line of credit facility potential maximum borrowing capacity					$ 400,000,000
Balances outstanding under the revolving credit facility					55,000,000
Available financing of receivables purchase agreement	70,000,000					70,000,000		50,000,000
Letters of credit outstanding		30,600,000
Interest at a rate					1.5
Liquidity commitments under the receivables purchase agreement renewed day							1 year
Debt due within one year			0	0
Long-term debt net of unamortized discounts		0	0	20,900,000
Fair value of the traded debt									247,100,000	239,600,000	237,800,000	55,000,000
Quoted market prices of Corporation's publicly traded debt, carrying value		$ 280,181,000	$ 225,181,000	$ 233,970,000					$ 225,200,000	$ 225,200,000	$ 234,000,000	$ 55,000,000