Long-Term Debt - Schedule (Details)		3 Months Ended
	Mar. 01, 2016 USD ($)	May 31, 2016 USD ($) item	May 31, 2015 USD ($)	Feb. 29, 2016 USD ($)
Long-term debt
Total long-term debt		$ 587,491,000		$ 619,914,000
Less current maturities of long-term debt		(24,540,000)		(22,644,000)
Long-term debt, excluding current maturities		562,951,000		597,270,000
Principal payment made		3,800,000	$ 1,900,000
Unsecured state industrial development loan
Long-term debt
Total long-term debt		29,908,000		33,706,000
Principal payment made	$ 3,800,000
Outstanding principal payable on March 1, 2017		5,700,000
Outstanding principal payable on March 1, 2018		1,900,000
Outstanding principal payable on March 1, 2019		1,900,000
Outstanding principal payable on March 1, 2020		1,900,000
Outstanding principal payable on March 1, 2021		1,900,000
Outstanding principal payable on March 1, 2022		1,900,000
Outstanding principal payable on March 1, 2023		14,810,000
Unsecured state industrial development loan | Base Rate Loan
Long-term debt
Face amount		$ 37,610,000
Unsecured state industrial development loan | Maximum | Base Rate
Long-term debt
Margin (as a percent)		1.00%
Unsecured state industrial development loan | Maximum | LIBOR
Long-term debt
Margin (as a percent)		2.00%
3.90% unsecured Senior Notes payable
Long-term debt
Face amount		$ 100,000,000
Interest rate (as a percent)		3.90%
Fixed interest rate (as a percentage)		3.90%
Principal payment		$ 20,000,000
Total long-term debt		39,553,000		39,496,000
Credit Agreement
Long-term debt
Maximum revolving commitment		$ 650,000,000
Number of alternative methods under which interest on borrowings accrue | item		2
Amount available for borrowings		$ 127,300,000
Total long-term debt		518,030,000		$ 546,712,000
Revolving loan | Credit Agreement
Long-term debt
Amount outstanding		521,200,000
Letter of credit | Credit Agreement
Long-term debt
Amount outstanding		$ 1,500,000