Commitments (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Nov. 30, 2011
Estimated time period for commissioning after restart of construction, in months	24
Incurred capital cost excluding capitalized interest	$ 335.0
Interest costs incurred related to the project	51.1
Capital expenditure excluding capitalized interest	324.3
Minimum [Member]
Expected total capital cost of project excluding capitalized interest	365
Maximum [Member]
Expected total capital cost of project excluding capitalized interest	$ 375