Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Cash flows from operating activities
Net income	$ 126,820	$ 103,814	$ 114,694
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	131,160	111,823	96,552
Other amortization	297	195	347
Stock-based compensation	5,600	4,270	3,792
Loss on disposal of assets and impairment charges	2,846	4,788	1,428
Deferred income taxes	17,089	31,828	53,141
Excess tax benefits related to stock option exercises	(1,791)	(1,929)	(1,162)
Changes in assets and liabilities:
Receivables	(4,941)	800	(1,546)
Inventories	(13,696)	(16,222)	(8,647)
Prepaid expenses	(82)	(98)	(118)
Accounts payable	17,894	21,748	(4,510)
Accrued expenses	33,818	15,783	10,944
Income taxes receivable	(441)	9,969	29,508
Other, net	(413)	(441)	456
Net cash provided by operating activities	314,160	286,328	294,879
Cash flows from investing activities
Purchase of property and equipment	(308,633)	(305,301)	(240,874)
Payments for acquisitions of businesses, net of cash acquired	(31,584)	(29,527)	(39,444)
Proceeds from sales of property and equipment	3,328	3,544	2,196
Net cash used in investing activities	(336,889)	(331,284)	(278,122)
Cash flows from financing activities
Proceeds from long-term debt	200,000	0	0
Repayments of long-term debt	(15,865)	(10,757)	(1,372)
Net (repayments) borrowings of short-term debt	(59,100)	59,100	(600)
Proceeds from exercise of stock options	3,368	4,721	3,249
Payments of cash dividends	(27,095)	(24,685)	(22,849)
Excess tax benefits related to stock option exercises	1,791	1,929	1,162
Net cash provided by (used in) financing activities	103,099	30,308	(20,410)
Net increase (decrease) in cash and cash equivalents	80,370	(14,648)	(3,653)
Cash and cash equivalents at beginning of year	41,271	55,919	59,572
Cash and cash equivalents at end of year	121,641	41,271	55,919
Cash paid (received) during the year for
Interest, net of amount capitalized	36,923	35,226	35,403
Income taxes	50,031	17,973	(17,973)
Noncash investing and financing activities
Property and equipment acquired through notes payable and capitalized lease obligations	$ 1,169	$ 981	$ 191