Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Oct. 31, 2014	Oct. 31, 2013
Cash flows from operating activities:
Net income	$ 99,966	$ 93,225
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	73,524	62,917
Other amortization	198	162
Stock based compensation	2,667	2,420
Loss on disposal of assets and impairment charges	132	2,063
Deferred income taxes	4,451	8,633
Excess tax benefits related to stock option exercises	(1,146)	(1,485)
Changes in assets and liabilities:
Receivables	(5,193)	(4,656)
Inventories	7,594	(8,993)
Prepaid expenses	(1,196)	(799)
Accounts payable	(25,357)	(2,627)
Accrued expenses	3,872	19,277
Income taxes	23,974	15,357
Other, net	(94)	(185)
Net cash provided by operating activities	183,392	185,309
Cash flows from investing activities:
Purchase of property and equipment	(195,682)	(162,882)
Payments for acquisition of businesses, net of cash acquired	(34,288)	(24,542)
Proceeds from sales of property and equipment	1,783	734
Net cash used in investing activities	(228,187)	(186,690)
Cash flows from financing activities:
Proceeds from long-term debt		150,000
Repayments of long-term debt	(361)	(7,925)
Net repayments of short-term debt		(59,100)
Proceeds from exercise of stock options	8,571	2,758
Payments of cash dividends	(14,652)	(13,840)
Excess tax benefits related to stock option exercises	1,146	1,485
Net cash (used in) provided by financing activities	(5,296)	73,378
Net (decrease) increase in cash and cash equivalents	(50,091)	71,997
Cash and cash equivalents at beginning of the period	121,641	41,271
Cash and cash equivalents at end of the period	71,550	113,268
Cash paid during the period for:
Interest, net of amount capitalized	20,954	17,389
Income taxes	$ 30,251	$ 29,680