Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Oct. 31, 2016	Oct. 31, 2015
Cash flows from operating activities:
Net income	$ 124,572	$ 140,839
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	94,530	81,206
Other amortization	199	210
Stock-based compensation	4,948	3,373
Loss (gain) on disposal of assets and impairment charges	294	(191)
Deferred income taxes	19,839	(3,191)
Changes in assets and liabilities:
Receivables	(5,229)	(9,316)
Inventories	(2,854)	(6,946)
Prepaid expenses	(1,952)	(838)
Accounts payable	(3,239)	2,401
Accrued expenses	(1,221)	8,975
Income taxes	13,238	33,930
Other, net	(3,041)	(176)
Net cash provided by operating activities	240,084	250,276
Cash flows from investing activities:
Purchase of property and equipment	(203,602)	(209,948)
Payments for acquisition of businesses, net of cash acquired	(5,596)	0
Proceeds from sales of property and equipment	1,726	2,541
Net cash used in investing activities	(207,472)	(207,407)
Cash flows from financing activities:
Proceeds from long-term debt	100,000	0
Repayments of long-term debt	(7,697)	(7,697)
Proceeds from exercise of stock options	1,719	2,089
Payments of cash dividends	(17,988)	(16,322)
Tax withholdings on employee share-based awards	(6,448)	(3,900)
Net cash provided by (used in) financing activities	69,586	(25,830)
Net increase in cash and cash equivalents	102,198	17,039
Cash and cash equivalents at beginning of the period	75,775	48,541
Cash and cash equivalents at end of the period	177,973	65,580
Cash paid during the period for:
Interest, net of amount capitalized	20,065	20,206
Income taxes, net	33,038	49,731
Noncash investing and financing activities:
Purchased property and equipment in accounts payable	$ 12,980	$ 17,077