Business Segments (Summary Of Operating Results And Certain Other Financial Data For Business Segments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2011	Nov. 30, 2010	Nov. 30, 2011	Nov. 30, 2010
Net sales	$ 156,071	$ 148,111	$ 337,811	$ 320,233
Segment operating profit (loss)	(6,861)	2,888	1,231	12,737
Corporate	(5,959)	(7,435)	(12,158)	(12,427)
Interest	(8,838)	(13,886)	(18,298)	(28,297)
Loss on debt retirements		(613)		(29,619)
Loss before income taxes	(21,658)	(19,046)	(29,225)	(57,606)
Depreciation, depletion and amortization	15,405	16,130	31,385	31,991
Capital expenditures	16,678	20,243	62,266	23,399
Cement [Member]
Sales to external customers	65,639	57,138	137,697	120,373
Intersegment sales	11,595	11,440	25,174	24,587
Segment operating profit (loss)	(5,355)	1,948	1,162	5,912
Depreciation, depletion and amortization	8,897	9,181	17,824	18,330
Capital expenditures	14,193	10,832	39,889	12,579
Aggregates [Member]
Sales to external customers	33,013	34,759	72,514	77,833
Intersegment sales	6,953	6,323	12,553	13,219
Segment operating profit (loss)	2,100	3,323	6,015	8,457
Depreciation, depletion and amortization	3,868	4,956	8,063	9,728
Capital expenditures	1,237	3,727	19,542	4,904
Consumer Products [Member]
Sales to external customers	57,419	56,214	127,600	122,027
Intersegment sales	702	606	1,545	1,271
Segment operating profit (loss)	(3,606)	(2,383)	(5,946)	(1,632)
Depreciation, depletion and amortization	2,326	1,709	4,890	3,365
Capital expenditures	611	5,271	2,042	5,467
Corporate [Member]
Depreciation, depletion and amortization	314	284	608	568
Capital expenditures	637	413	793	449
Segment Eliminations [Member]
Net sales	(19,250)	(18,369)	(39,272)	(39,077)
Cement Products [Member]
Net sales	57,400	50,197	119,799	104,747
Stone, Sand And Gravel [Member]
Net sales	15,257	17,577	32,532	38,054
Ready-Mix Concrete [Member]
Net sales	44,578	43,347	100,801	95,431
Other Products [Member]
Net sales	21,120	21,242	46,735	47,122
Delivery Fees [Member]
Net sales	$ 17,716	$ 15,748	$ 37,944	$ 34,879