Fair Value (Financial Assets and Liabilities Not Required to Be Measured at Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2013		Aug. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt and Capital Lease Obligations	$ 1,154,479		$ 1,161,325
$200 million notes at 5.625% due November 2013 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt and Capital Lease Obligations	202,857		204,873
$200 million notes at 5.625% due November 2013 [Member] | Level 2 [Member] | Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt and Capital Lease Obligations	202,857	[1]	204,873	[1]
$200 million notes at 5.625% due November 2013 [Member] | Level 2 [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt and Capital Lease Obligations	208,607	[1]	212,413	[1]
$400 million notes at 6.50% due July 2017 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt and Capital Lease Obligations	413,005		414,491
$400 million notes at 6.50% due July 2017 [Member] | Level 2 [Member] | Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt and Capital Lease Obligations	413,005	[1]	414,491	[1]
$400 million notes at 6.50% due July 2017 [Member] | Level 2 [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt and Capital Lease Obligations	444,341	[1]	434,991	[1]
$500 million notes at 7.35% due August 2018 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt and Capital Lease Obligations	525,241		527,554
$500 million notes at 7.35% due August 2018 [Member] | Level 2 [Member] | Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt and Capital Lease Obligations	525,241	[1]	527,554	[1]
$500 million notes at 7.35% due August 2018 [Member] | Level 2 [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt and Capital Lease Obligations	$ 569,791	[1]	$ 559,894	[1]

[1] (1) The fair value of the notes is calculated based on indicated market values.