Business Segments (Summary Of Assets Used In Each Business Segments) (Details) (USD $) In Thousands, unless otherwise specified	Nov. 30, 2011	May 31, 2011
Identifiable assets	$ 1,525,041	$ 1,551,011
Cement [Member]
Identifiable assets	1,102,166	1,082,524
Aggregates [Member]
Identifiable assets	215,984	201,917
Consumer Products [Member]
Identifiable assets	96,124	106,643
Corporate [Member]
Identifiable assets	$ 110,767	$ 159,927