Business Segment Information (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	May 31, 2014	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2014	May 31, 2013	May 31, 2012
Business Segment Information
Long-lived assets	$ 1,082.6				$ 1,103.2				$ 1,082.6	$ 1,103.2
Sales	505.4	474.4	540.7	514.5	553.8	520.2	512.8	550.5	2,035.0	2,137.3	2,065.0
United States
Business Segment Information
Long-lived assets	809.0				834.1				809.0	834.1
Europe
Business Segment Information
Long-lived assets	271.4				267.2				271.4	267.2
Other
Business Segment Information
Long-lived assets	2.2				1.9				2.2	1.9
Foreign countries
Business Segment Information
Sales									$ 668.4	$ 656.5	$ 435.7
Foreign countries | Total sales | Geographic concentration
Business Segment Information
Percentage of total sales									32.80%	30.70%	21.10%