Employee Benefit Plans (Details) - Summary of weighted average actuarial assumptions utilized to benefit obligations	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Weighted average assumptions used to determine net periodic benefit cost:
Expected long-term return on plan assets	7.50%
Pension Plans [Member]
Weighted average assumptions used to determine benefit obligations:
Discount rate	4.10%	4.00%	4.00%
Rate of compensation increase	4.20%	4.40%	3.30%
Weighted average assumptions used to determine net periodic benefit cost:
Discount rate	4.00%	4.00%	5.10%
Expected long-term return on plan assets	7.50%	7.30%	7.70%
Rate of compensation increase	4.40%	3.30%	4.30%
Other Postretirement Benefits [Member]
Weighted average assumptions used to determine benefit obligations:
Discount rate	4.00%	3.90%	3.90%
Rate of compensation increase	0.00%	0.00%	0.00%
Weighted average assumptions used to determine net periodic benefit cost:
Discount rate	3.90%	3.90%	5.00%
Expected long-term return on plan assets	0.00%	0.00%	0.00%
Rate of compensation increase	0.00%	0.00%	0.00%