Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2016	Jul. 31, 2015
Cash flows from operating activities:
Net income	$ 67,392	$ 61,806
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	45,855	39,399
Other amortization	126	110
Stock based compensation	2,471	1,737
Gain on disposal of assets and impairment charges	(302)	(259)
Deferred income taxes	11,840	(1,617)
Excess tax benefits related to stock option exercises	0	(1,140)
Changes in assets and liabilities:
Receivables	(4,392)	(11,045)
Inventories	(631)	(17,998)
Prepaid expenses	(2,524)	(2,598)
Accounts payable	16,976	3,402
Accrued expenses	12,896	6,687
Income taxes	12,215	26,986
Other, net	(573)	(107)
Net cash provided by operating activities	161,349	105,363
Cash flows from investing activities:
Purchase of property and equipment	(82,296)	(100,141)
Payments for acquisition of businesses, net of cash acquired	(2,854)	0
Proceeds from sales of property and equipment	932	1,288
Net cash used in investing activities	(84,218)	(98,853)
Cash flows from financing activities:
Proceeds from long-term debt	50,000	0
Repayments of long-term debt	(98)	(98)
Proceeds from exercise of stock options	1,598	1,805
Payments of cash dividends	(8,577)	(7,726)
Payments of cash dividends	0	1,140
Tax withholdings on employee share-based awards	(6,339)	(3,567)
Net cash provided by (used in) financing activities	36,584	(8,446)
Net increase (decrease) in cash and cash equivalents	113,715	(1,936)
Cash and cash equivalents at beginning of the period	75,775	48,541
Cash and cash equivalents at end of the period	189,490	46,605
Cash paid during the period for:
Interest, net of amount capitalized	3,785	3,471
Income taxes, net	9,793	10,749
Noncash investing and financing activities:
Purchased property and equipment in accounts payable	$ 11,664	$ 13,203