Processing System Instrusion (Details) (USD $)	12 Months Ended
	May 31, 2012	May 31, 2011	May 31, 2010
Processing System Intrusion [Abstract]
Processing system intrusion	$ 84,438,000	$ 0	$ 0
Payments for processing system intrusion costs	19,000,000
Accrued processing system intrusion fines	67,400,000
Insurance reimbursements receivable for claims submitted to date	2,000,000
Insurance carried, policy limits	30,000,000
Insurance carried, deductible amount per claim	$ 1,000,000