Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Cash flows from operating activities
Net income	$ 225,982	$ 180,628	$ 126,820
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	170,937	156,111	131,160
Stock-based compensation	7,413	7,307	5,600
Loss on disposal of assets and impairment charges	837	2,370	2,846
Deferred income taxes	55,492	44,711	17,089
Excess tax benefits related to stock option exercises	(2,702)	(3,624)	(1,791)
Changes in assets and liabilities:
Receivables	(5,092)	3,232	(4,941)
Inventories	(7,390)	10,365	(13,696)
Prepaid expenses	(983)	(547)	(82)
Accounts payable	3,011	(33,290)	17,894
Accrued expenses	10,008	(17,544)	33,818
Income taxes receivable	7,064	(7,801)	(441)
Other, net	132	(236)	(116)
Net cash provided by operating activities	464,709	341,682	314,160
Cash flows from investing activities
Purchase of property and equipment	(392,839)	(360,734)	(308,633)
Payments for acquisitions of businesses, net of cash acquired	(7,263)	(41,157)	(31,584)
Proceeds from sales of property and equipment	5,134	2,748	3,328
Net cash used in investing activities	(394,968)	(399,143)	(336,889)
Cash flows from financing activities
Proceeds from long-term debt	0	0	200,000
Repayments of long-term debt	(15,399)	(553)	(15,865)
Net (repayments) borrowings of short-term debt	0	0	(59,100)
Proceeds from exercise of stock options	3,717	11,465	3,368
Payments of cash dividends	(33,527)	(30,175)	(27,095)
Excess tax benefits related to stock option exercises	2,702	3,624	1,791
Net cash (used in) provided by financing activities	(42,507)	(15,639)	103,099
Net increase (decrease) in cash and cash equivalents	27,234	(73,100)	80,370
Cash and cash equivalents at beginning of year	48,541	121,641	41,271
Cash and cash equivalents at end of year	75,775	48,541	121,641
SUPPLEMENTAL DISCLOSURES OF CASH FLOWS INFORMATION
Cash paid during the year for interest, net of amount capitalized	40,401	41,382	36,923
Cash paid for income taxes, net	60,049	64,367	50,031
Noncash investing and financing activities
Purchased property and equipment in accounts payable	11,619	9,060	5,056
Property and equipment acquired through notes payable and capitalized lease obligations	$ 0	$ 0	$ 1,169