Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Jan. 31, 2016	Jan. 31, 2015
Cash flows from operating activities:
Net income	$ 178,938	$ 139,285
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	125,028	113,955
Other amortization	310	260
Stock based compensation	5,793	6,292
Loss on disposal of assets and impairment charges	314	584
Deferred income taxes	41,551	27,631
Excess tax benefits related to stock option exercises	(2,563)	(3,014)
Changes in assets and liabilities:
Receivables	(1,331)	3,624
Inventories	7,744	39,228
Prepaid expenses	(1,644)	(1,428)
Accounts payable	(33,193)	(80,747)
Accrued expenses	13,962	(16,580)
Income taxes	7,523	10,986
Other, net	(348)	(216)
Net cash provided by operating activities	342,084	239,860
Cash flows from investing activities:
Purchase of property and equipment	(312,588)	(292,144)
Payments for acquisition of businesses, net of cash acquired	(4,252)	(37,073)
Proceeds from sales of property and equipment	3,546	2,158
Net cash used in investing activities	(313,294)	(327,059)
Cash flows from financing activities:
Repayments of long-term debt	(7,797)	(456)
Net borrowings of short-term debt	2,800	18,500
Proceeds from exercise of stock options	3,595	10,535
Payments of cash dividends	(24,929)	(22,398)
Excess tax benefits related to stock option exercises	2,563	3,014
Net cash (used in) provided by financing activities	(23,768)	9,195
Net increase (decrease) in cash and cash equivalents	5,022	(78,004)
Cash and cash equivalents at beginning of the period	48,541	121,641
Cash and cash equivalents at end of the period	53,563	43,637
Cash paid during the period for:
Interest, net of amount capitalized	23,125	24,536
Income taxes, net	50,862	42,352
Noncash investing and financing activities:
Purchased property and equipment in accounts payable	$ 13,256	$ 4,644