Employee Benefit Plans (Details 2) (Defined Benefit Pension Plans, USD $) In Millions, unless otherwise specified																								12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012	May 31, 2014 Quoted prices in active markets (Level 1)	May 31, 2013 Quoted prices in active markets (Level 1)	May 31, 2014 Quoted prices in active markets (Level 1) U.S. common stock	May 31, 2013 Quoted prices in active markets (Level 1) U.S. common stock	May 31, 2014 Quoted prices in active markets (Level 1) U.S. mutual funds	May 31, 2013 Quoted prices in active markets (Level 1) U.S. mutual funds	May 31, 2014 Quoted prices in active markets (Level 1) International common stock	May 31, 2013 Quoted prices in active markets (Level 1) International common stock	May 31, 2014 Quoted prices in active markets (Level 1) International mutual funds	May 31, 2013 Quoted prices in active markets (Level 1) International mutual funds	May 31, 2014 Quoted prices in active markets (Level 1) Government securities mutual funds	May 31, 2013 Quoted prices in active markets (Level 1) Government securities mutual funds	May 31, 2014 Quoted prices in active markets (Level 1) Corporate bonds mutual funds	May 31, 2013 Quoted prices in active markets (Level 1) Corporate bonds mutual funds	May 31, 2014 Quoted prices in active markets (Level 1) Cash and cash equivalents	May 31, 2013 Quoted prices in active markets (Level 1) Cash and cash equivalents	May 31, 2014 Significant other observable inputs (Level 2)	May 31, 2013 Significant other observable inputs (Level 2)	May 31, 2014 Significant other observable inputs (Level 2) Funds-of-funds	May 31, 2013 Significant other observable inputs (Level 2) Funds-of-funds	May 31, 2014 Significant other unobservable inputs (Level 3)	May 31, 2013 Significant other unobservable inputs (Level 3)	May 31, 2014 Significant other unobservable inputs (Level 3) Hedge funds	May 31, 2013 Significant other unobservable inputs (Level 3) Hedge funds	May 31, 2014 Significant other unobservable inputs (Level 3) Funds-of-funds	May 31, 2013 Significant other unobservable inputs (Level 3) Funds-of-funds	May 31, 2014 Total	May 31, 2013 Total	May 31, 2014 Total U.S. common stock	May 31, 2013 Total U.S. common stock	May 31, 2014 Total U.S. mutual funds	May 31, 2013 Total U.S. mutual funds	May 31, 2014 Total International common stock	May 31, 2013 Total International common stock	May 31, 2014 Total International mutual funds	May 31, 2013 Total International mutual funds	May 31, 2014 Total Government securities mutual funds	May 31, 2013 Total Government securities mutual funds	May 31, 2014 Total Corporate bonds mutual funds	May 31, 2013 Total Corporate bonds mutual funds	May 31, 2014 Total Hedge funds	May 31, 2013 Total Hedge funds	May 31, 2014 Total Funds-of-funds	May 31, 2013 Total Funds-of-funds	May 31, 2014 Total Cash and cash equivalents	May 31, 2013 Total Cash and cash equivalents
Employee benefit plans
Fair value of plan assets	$ 116.0	$ 101.6	$ 87.7	$ 54.3	$ 47.4	$ 6.5	$ 6.1	$ 24.0	$ 21.7	$ 0.6	$ 0.7	$ 9.1	$ 6.7	$ 7.4	$ 7.2	$ 3.6	$ 4.0	$ 3.1	$ 1.0	$ 50.6	$ 44.1	$ 50.6	$ 44.1	$ 11.1	$ 10.1	$ 3.6	$ 2.4	$ 7.5	$ 7.7	$ 116.0	$ 101.6	$ 6.5	$ 6.1	$ 24.0	$ 21.7	$ 0.6	$ 0.7	$ 9.1	$ 6.7	$ 7.4	$ 7.2	$ 3.6	$ 4.0	$ 3.6	$ 2.4	$ 58.1	$ 51.8	$ 3.1	$ 1.0
Reconciliation of pension assets measured at fair value
Fair value of plan assets at beginning of year	116.0	101.6	87.7	54.3	47.4	6.5	6.1	24.0	21.7	0.6	0.7	9.1	6.7	7.4	7.2	3.6	4.0	3.1	1.0	50.6	44.1	50.6	44.1	10.1	9.4	2.4	2.3	7.7	7.1	116.0	101.6	6.5	6.1	24.0	21.7	0.6	0.7	9.1	6.7	7.4	7.2	3.6	4.0	3.6	2.4	58.1	51.8	3.1	1.0
Sales																								(4.7)		(2.4)		(2.3)
Purchases																								5.4		3.6		1.8
Return on plan assets related to:
Assets sold																								(0.3)				(0.3)
Relating to assets still held at reporting date																								0.6	0.7		0.1	0.6	0.6
Fair value of plan assets at end of year	$ 116.0	$ 101.6	$ 87.7	$ 54.3	$ 47.4	$ 6.5	$ 6.1	$ 24.0	$ 21.7	$ 0.6	$ 0.7	$ 9.1	$ 6.7	$ 7.4	$ 7.2	$ 3.6	$ 4.0	$ 3.1	$ 1.0	$ 50.6	$ 44.1	$ 50.6	$ 44.1	$ 11.1	$ 10.1	$ 3.6	$ 2.4	$ 7.5	$ 7.7	$ 116.0	$ 101.6	$ 6.5	$ 6.1	$ 24.0	$ 21.7	$ 0.6	$ 0.7	$ 9.1	$ 6.7	$ 7.4	$ 7.2	$ 3.6	$ 4.0	$ 3.6	$ 2.4	$ 58.1	$ 51.8	$ 3.1	$ 1.0