Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Jan. 31, 2014	Jan. 31, 2013
Cash flows from operations:
Net income	$ 111,698	$ 87,353
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and amortization	95,604	81,913
Other amortization	223	159
Stock based compensation	4,001	3,165
Loss on disposal of assets and impairment charges	2,880	4,272
Deferred income taxes	14,030	29,098
Excess tax benefits related to stock option exercises	(1,615)	(1,682)
Changes in assets and liabilities:
Receivables	(4,167)	1,910
Inventories	84	(12,087)
Prepaid expenses	(696)	(655)
Accounts payable	(31,101)	(13,920)
Accrued expenses	18,933	11,969
Income taxes	1,028	3,682
Other, net	(216)	(638)
Net cash provided by operations	210,686	194,539
Cash flows from investing:
Purchase of property and equipment	(242,548)	(241,126)
Payments for acquisition of stores, net of cash acquired	(26,583)	(25,198)
Proceeds from sale of property and equipment	2,219	2,421
Net cash used in investing activities	(266,912)	(263,903)
Cash flows from financing:
Proceeds from long-term debt	200,000
Payments of long-term debt	(8,144)	(5,562)
Net (payments) borrowings of short-term debt	(59,100)	58,600
Proceeds from exercise of stock options	2,912	4,209
Payments of cash dividends	(20,168)	(18,963)
Excess tax benefits related to stock option exercises	1,615	1,682
Net cash provided by financing activities	117,115	39,966
Net increase (decrease) in cash and cash equivalents	60,889	(29,398)
Cash and cash equivalents at beginning of the period	41,271	55,919
Cash and cash equivalents at end of the period	102,160	26,521
Cash paid during the period for:
Interest, net of amount capitalized	19,969	17,637
Income taxes	48,960	18,280
Noncash investing and financing activities
Property and equipment acquired through capitalized lease obligations	$ 1,169	$ 981