Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Cash flows from operating activities:
Net income	$ 56,758	$ 67,392
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	52,369	45,855
Stock-based compensation	9,807	2,471
Loss (gain) on disposal of assets and impairment charges	140	(302)
Deferred income taxes	15,564	11,840
Changes in assets and liabilities:
Receivables	(1,300)	(4,392)
Inventories	(24,244)	(631)
Prepaid expenses	928	(2,524)
Accounts payable	(20,010)	16,976
Accrued expenses	8,284	12,896
Income taxes	18,899	12,215
Other, net	(56)	(447)
Net cash provided by operating activities	117,139	161,349
Cash flows from investing activities:
Purchase of property and equipment	(91,548)	(82,296)
Payments for acquisition of businesses, net of cash acquired	(3,322)	(2,854)
Proceeds from sales of property and equipment	1,607	932
Net cash used in investing activities	(93,263)	(84,218)
Cash flows from financing activities:
Proceeds from long-term debt	150,000	50,000
Repayments of long-term debt	(103)	(98)
Net repayments of short-term debt	(900)	0
Proceeds from exercise of stock options	195	1,598
Payments of cash dividends	(9,312)	(8,577)
Repurchase of common stock	(77,878)	0
Tax withholdings on employee share-based awards	(3,494)	(6,339)
Net cash provided by financing activities	58,508	36,584
Net increase in cash and cash equivalents	82,384	113,715
Cash and cash equivalents at beginning of the period	76,717	75,775
Cash and cash equivalents at end of the period	159,101	189,490
Cash paid during the period for:
Interest, net of amount capitalized	4,673	3,785
Income taxes, net	463	9,793
Noncash investing and financing activities:
Purchased property and equipment in accounts payable	$ 7,752	$ 11,664