Income Tax - Narrative (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended				3 Months Ended		9 Months Ended		12 Months Ended
	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014 Other Noncurrent Liabilities [Member]	May 31, 2013 Other Noncurrent Liabilities [Member]	Feb. 28, 2014 United Kingdom [Member] Foreign Tax Authority [Member]	Feb. 28, 2013 United Kingdom [Member] Foreign Tax Authority [Member]	Feb. 28, 2014 United Kingdom [Member] Foreign Tax Authority [Member]	Feb. 28, 2013 United Kingdom [Member] Foreign Tax Authority [Member]	May 24, 2010 HSBC Merchant Services LLP [Member]
Income Tax Contingency [Line Items]
Deferred tax asset related primarily to HSBC Merchant Services LLP	$ 95.7		$ 95.7
Remaining noncontrolling interest purchased by parent, percentage											49.00%
Effective tax rate	28.30%	27.20%	28.40%	28.60%
Effective income tax rate reconciliation, change in enacted tax rate							3.00%	2.00%	3.00%	2.00%
Unrecognized tax benefits					65.2	53.8
Increase in unrecognized tax benefits	$ 3.0		$ 11.4