Business Segments - Additional Information (Detail) (USD $)	9 Months Ended
	Feb. 28, 2014 Segment	Feb. 28, 2013
Segment Reporting Information [Line Items]
Number of operating business segments	3
Upgrades of existing equipment and acquisitions	$ 26,152,000	$ 17,752,000
Capital expenditure incurred for expansion	7,125,000	61,344,000
Hunter Cement Plant
Segment Reporting Information [Line Items]
Capital expenditure incurred for expansion	7,100,000	61,300,000
Capitalized interest paid		$ 38,500,000
Maximum
Segment Reporting Information [Line Items]
Sales percentage represented by major customers	10.00%	10.00%
Net Sales
Segment Reporting Information [Line Items]
Number of customers exceeding 10% threshold	0	0