Goodwill, Service Contracts and Other Assets (Narrative) (Details) (USD $)	3 Months Ended
	Aug. 31, 2013	Aug. 31, 2012
Goodwill, Service Contracts and Other Assets [Abstract]
Amortization expense	$ 5,823,000	$ 6,100,000
Estimated amortization expense, year one	22,400,000
Estimated amortization expense, year two	19,600,000
Estimated amortization expense, year three	14,300,000
Estimated amortization expense, year four	9,100,000
Estimated amortization expense, year five	7,900,000
Cost method investments, losses due to impairment	$ 0	$ 0