Debt (Details) (USD $)	6 Months Ended
	Feb. 29, 2012	Aug. 31, 2011	Feb. 28, 2011
Short-term Debt [Line Items]
Total short-term borrowings	$ 12,000,000	$ 13,000,000	$ 13,000,000
Letters of credit issued	0
Debt Instrument [Line Items]
Total-long term debt	2,381,000,000	2,396,000,000	2,380,000,000
Line of Credit Facility [Line Items]
Covenant Terms	The covenants require the Company to maintain certain financial ratios related to minimum net worth and priority debt, along with limitations on the sale of assets and purchases of investments.
Covenant compliance	At February 29, 2012, the Company was in compliance with all such covenants.
Facility fee description	The Company pays a facility fee to the financing banks to keep these lines of credit active
Letters of credit issued	0
Syndicated lines of credit one [Member]
Line of Credit Facility [Line Items]
Line of credit facility description	The first $500 million facility expires on July 20, 2015, and allows for the issuance of up to $250 million in letters of credit, which reduces the amount available for borrowing.
Maximum borrowing capacity	500,000,000
Expiration date	July 20, 2015
Syndicated lines of credit two [Member]
Line of Credit Facility [Line Items]
Line of credit facility description	The second $600 million facility expires on August 13, 2012.
Maximum borrowing capacity	600,000,000
Expiration date	August 13, 2012
Unsecured Debt [Member] | Notes due 2013 [Member]
Debt Instrument [Line Items]
Carrying value of notes, net of discount and FMV adjustment, if applicable	1,320,000,000	1,339,000,000	1,338,000,000
Stated Interest Rate	4.875%
Maturity Date	Aug. 01, 2013
Issuance date	July 17 2008
Face amount of notes issued	1,300,000,000
Interest payment frequency	semiannually
Date of first payment	Feb. 01, 2009
Call feature	The Company may redeem the notes, at any time in whole or from time to time in part, at its option at a redemption price equal to the greater of: (1) 100% of the principal amount of the notes to be redeemed; or (2) the sum of the present values of the remaining scheduled payments of principal and interest, discounted to the date of redemption on a semiannual basis at the Treasury Rate, plus 30 basis points, plus accrued interest on the notes to be redeemed to, but excluding, the date of redemption. If a change of control triggering event occurs, unless the Company has exercised its option to redeem the notes, it will be required to offer to repurchase the notes at a purchase price equal to 101% of the principal amount of the notes plus accrued and unpaid interest to the date of redemption.
Percentage of principal amount of notes company may redeem	100.00%
Basis points added to treasury rate to calculate redemption rate	30
Required purchase price on triggering event	101.00%
Total issuance costs	9,000,000
Underwriting fees included in total issuance costs	8,000,000
Debt instrument fair value	1,383,000,000	1,403,000,000	1,412,000,000
Basis for fair value measurement	Fair value for these notes was determined based upon quoted market prices.
Unsecured Debt [Member] | Notes due 2019 [Member]
Debt Instrument [Line Items]
Carrying value of notes, net of discount and FMV adjustment, if applicable	1,015,000,000	1,011,000,000	996,000,000
Stated Interest Rate	5.25%
Maturity Date	Jan. 15, 2019
Issuance date	January 13 2009
Face amount of notes issued	1,000,000,000
Interest payment frequency	semiannually
Date of first payment	Jul. 15, 2009
Call feature	The Company may redeem the notes, at any time in whole or from time to time in part, at its option at a redemption price equal to the greater of: (1) 100% of the principal amount of the notes to be redeemed; or (2) the sum of the present values of the remaining scheduled payments of principal and interest, discounted to the date of redemption on a semiannual basis at the Treasury Rate, plus 45 basis points, plus accrued interest on the notes to be redeemed to, but excluding, the date of redemption. If a change of control triggering event occurs, unless the Company has exercised its option to redeem the notes, it will be required to offer to repurchase the notes at a purchase price equal to 101% of the principal amount of the notes plus accrued and unpaid interest to the date of redemption.
Percentage of principal amount of notes company may redeem	100.00%
Basis points added to treasury rate to calculate redemption rate	45
Required purchase price on triggering event	101.00%
Total issuance costs	8,000,000
Underwriting fees included in total issuance costs	7,000,000
Debt instrument fair value	1,118,000,000	1,173,000,000	1,087,000,000
Basis for fair value measurement	Fair value for these notes was determined based upon quoted market prices.
Loans Payable [Member] | Assumed loans [Member]
Short-term Debt [Line Items]
Current maturities of loans assumed through the purchase of land, buildings and equipment	(8,000,000)	(8,000,000)	(9,000,000)
Debt Instrument [Line Items]
Carrying value of notes, net of discount and FMV adjustment, if applicable	54,000,000	54,000,000	55,000,000
Current maturities	(8,000,000)	(8,000,000)	(9,000,000)
Minimum interest rate	5.00
Maximum interest rate	8.75
Maturity Start Date	2015
Maturity End Date	2035
Loans Payable [Member]
Short-term Debt [Line Items]
Current maturities of loans assumed through the purchase of land, buildings and equipment	8,000,000	8,000,000	9,000,000
Debt Instrument [Line Items]
Current maturities	8,000,000	8,000,000	9,000,000
Total short-term borrowings [Member]
Short-term Debt [Line Items]
Other short term borrowings	$ 4,000,000	$ 5,000,000	$ 4,000,000