Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016
Cash flows from operating activities:
Net income	$ 147,407	$ 178,938
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	145,682	125,028
Other amortization	255	310
Stock-based compensation	7,356	5,793
Loss on disposal of assets and impairment charges	810	314
Deferred income taxes	27,400	41,551
Changes in assets and liabilities:
Receivables	(6,841)	(1,331)
Inventories	(4,061)	7,744
Prepaid expenses	(1,718)	(1,644)
Accounts payable	(20,755)	(33,193)
Accrued expenses	19,100	18,832
Income taxes	4,594	7,523
Other, net	(3,202)	(348)
Net cash provided by operating activities	316,027	349,517
Cash flows from investing activities:
Purchase of property and equipment	(325,609)	(312,588)
Payments for acquisition of businesses, net of cash acquired	(13,565)	(4,252)
Proceeds from sales of property and equipment	2,916	3,546
Net cash used in investing activities	(336,258)	(313,294)
Cash flows from financing activities:
Proceeds from long-term debt	100,000	0
Repayments of long-term debt	(7,797)	(7,797)
Net borrowings (repayments) of short-term debt	0	2,800
Proceeds from exercise of stock options	1,975	3,595
Payments of cash dividends	(27,407)	(24,929)
Tax withholdings on employee share-based awards	(6,594)	(4,870)
Net cash provided by (used in) financing activities	60,177	(31,201)
Net increase in cash and cash equivalents	39,946	5,022
Cash and cash equivalents at beginning of the period	75,775	48,541
Cash and cash equivalents at end of the period	115,721	53,563
Cash paid during the period for:
Interest, net of amount capitalized	24,430	23,125
Income taxes, net	46,861	50,862
Noncash investing and financing activities:
Purchased property and equipment in accounts payable	$ 10,020	$ 13,256