Pension and Postretirement Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013
Defined Benefit Pension Plan Disclosure [Line Items]
Curtailment (gain) loss	$ 0	$ 0	$ 0	$ 333
Pension Plans, Defined Benefit [Member]
Defined Benefit Pension Plan Disclosure [Line Items]
Service cost	960	988	1,908	1,954
Interest cost	1,355	1,222	2,689	2,423
Expected return on plan assets	(455)	(376)	(899)	(753)
Actuarial loss (gain) and amortization of prior service cost (credit), net	355	378	704	748
Net periodic benefit cost	2,215	2,212	4,402	4,372
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Pension Plan Disclosure [Line Items]
Service cost	1	3	2	8
Interest cost	123	112	246	227
Actuarial loss (gain) and amortization of prior service cost (credit), net	(141)	(136)	(280)	(270)
Curtailment (gain) loss	0	0	0	333
Net periodic benefit cost	$ (17)	$ (21)	$ (32)	$ 298