Employee Benefit Plans (Details) - Summary of weighted average actuarial assumptions utilized to benefit obligations	12 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2011
Weighted average assumptions used to determine net periodic benefit cost:
Expected long-term return on plan assets	7.30%
Pension Plan, Defined Benefit [Member]
Weighted average assumptions used to determine benefit obligations:
Discount rate	4.00%	4.00%	5.10%
Rate of compensation increase	4.40%	3.30%	4.30%
Weighted average assumptions used to determine net periodic benefit cost:
Discount rate	4.00%	5.10%	5.40%
Expected long-term return on plan assets	7.30%	7.70%	7.50%
Rate of compensation increase	3.30%	4.30%	4.30%
Other Postretirement Benefit Plan, Defined Benefit [Member]
Weighted average assumptions used to determine benefit obligations:
Discount rate	3.90%	3.90%	5.00%
Weighted average assumptions used to determine net periodic benefit cost:
Discount rate	3.90%	5.00%	5.40%