Summary of Fair Value of Assets Acquired and Liabilities Assumed At Acquisition Date (Detail) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2010
Assets:
Cash and cash equivalents	$ 7,983
Trade receivables	3,239
Prepaid expenses and other	254
Deposits and other	622
Property, plant and equipment, net (including construction-in-process)	129,764
Total identifiable assets acquired	141,862
Liabilities:
Current liabilities - accounts payable and accrued expenses	(1,072)
Asset retirement obligation	(3,342)
Total identifiable liabilities assumed	(4,414)
Total net assets acquired	$ 137,448