Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Oct. 31, 2012	Apr. 30, 2012
Assets [Abstract]
Cash and cash equivalents	$ 39,327	$ 55,919
Receivables	21,284	21,700
Inventories	178,298	170,794
Prepaid expenses	2,032	1,298
Deferred income taxes	10,604	13,143
Income tax receivable	8,286	16,424
Total current assets	259,831	279,278
Other assets, net of amortization	13,385	12,403
Goodwill	104,686	104,385
Property and equipment, net of accumulated depreciation of $901,517 at October 31, 2012 and $860,998 at April 30, 2012	1,483,659	1,378,749
Total assets	1,861,561	1,774,815
Liabilities and Shareholders' Equity [Abstract]
Current maturities of long-term debt	13,244	10,737
Accounts payable	215,213	211,165
Accrued expenses	86,272	84,739
Total current liabilities	314,729	306,641
Long-term debt, net of current maturities	660,055	667,930
Deferred income taxes	278,092	260,405
Deferred compensation	15,044	14,698
Other long-term liabilities	21,128	19,100
Total liabilities	1,289,048	1,268,774
Shareholders' equity:
Preferred stock, no par value
Common stock, no par value	19,419	12,199
Retained earnings	553,094	493,842
Total shareholders' equity	572,513	506,041
Total liabilities and shareholders' equity	$ 1,861,561	$ 1,774,815