Principal payments on the notes payable (Detail) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2012		Aug. 31, 2011
Project Debt Maturities Repayments Of Principal [Line Items]
2013	$ 73,469	[1]
2014	84,710
2015	42,183
2016	172
2017
Thereafter	230,000
Debt instrument face amount	$ 430,534		$ 434,854

[1] The repayment of the $67.7 million of Convertible senior notes due 2026 is assumed to occur in 2013, which is the first date holders can require the Company to repurchase all or a portion of the notes.