Pensions and Other Postretirement Benefits - Fair Value of Pension Plan's Assets by Major Asset Category (Detail) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2013	Aug. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 46,726	$ 42,072
Fair value of plan assets	46,726
Common collective trust funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44,378
Real estate equity funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,348
Fair value of plan assets	2,348	2,102
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Level 1 [Member] | Common collective trust funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Level 1 [Member] | Real estate equity funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44,378
Level 2 [Member] | Common collective trust funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44,378
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,348
Level 3 [Member] | Real estate equity funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2,348