Defined Contribution Plans (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
401(k) [Member]
Defined Benefit Plan Disclosure [Line Items]
Required years of service for plan eligibility (years)	1 year
Total contributions to defined benefit plans	$ 33.7	$ 28.4	$ 26.0
Deferred Profit Sharing Plan (DPSP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total contributions to defined benefit plans	1.6	1.4	1.3
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total contributions to defined benefit plans	$ 6.0	$ 4.7	$ 5.7