Fair Value Fair Value (Financial Assets And Liabilities Not Required To Be Measured At Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2013		Aug. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	$ 1,284,042		$ 1,161,325
$200 million notes at 5.625% due November 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	0		204,873
$200 million notes at 5.625% due November 2013 | Fair value, inputs, level 2 [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	0	[1]	204,873	[1]
$200 million notes at 5.625% due November 2013 | Fair value, inputs, level 2 [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	0	[1]	212,413	[1]
$400 million notes at 6.50% due July 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	411,518		414,491
$400 million notes at 6.50% due July 2017 | Fair value, inputs, level 2 [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	411,518	[1]	414,491	[1]
$400 million notes at 6.50% due July 2017 | Fair value, inputs, level 2 [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	443,646	[1]	434,991	[1]
$500 million notes at 7.35% due August 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	522,930		527,554
$500 million notes at 7.35% due August 2018 | Fair value, inputs, level 2 [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	522,930	[1]	527,554	[1]
$500 million notes at 7.35% due August 2018 | Fair value, inputs, level 2 [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	570,429	[1]	559,894	[1]
$330 million notes at 4.875% due May 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	330,000		0
$330 million notes at 4.875% due May 2023 | Fair value, inputs, level 2 [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	330,000	[1]	0	[1]
$330 million notes at 4.875% due May 2023 | Fair value, inputs, level 2 [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	$ 298,650	[1]	$ 0	[1]

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