Condensed Consolidated Statements of Comprehensive Income (Loss) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 1,191	$ (340)	$ 2,897	$ 252
Other comprehensive income (loss) net of tax:
Change in fair value of derivatives, net of tax benefit (expense) of $32, $(319), $(157), and $(152), respectively	(53)	521	256	248
Gain from derivative transactions reclassified into earnings, net of tax expense of $(95), $(221), $(1,434), and $(588), respectively	(155)	(360)	(2,341)	(961)
Amortization of prior service cost, net of taxes of $8, $0, $17, and $0, respectively	14		28
Amortization of actuarial loss, net of taxes of $209, $0, $418, and $0, respectively	341		682
Other comprehensive income (loss)	147	161	(1,375)	(713)
Total comprehensive income (loss)	$ 1,338	$ (179)	$ 1,522	$ (461)