Fair Value Measurements (Details) - Recurring [Member] - USD ($) $ in Millions		Nov. 30, 2016	Aug. 31, 2016
Restricted Cash [Member]
Assets [Abstract]
Fair value of assets	[1]	$ 174	$ 185
Money Market Funds [Member]
Assets [Abstract]
Fair value of assets	[2]	8,624	9,133
Available-for-sale Investments [Member]
Assets [Abstract]
Fair value of assets	[3]	28	32
Interest Rate Swaps [Member]
Assets [Abstract]
Fair value of assets	[4]		3
Foreign Currency Forwards [Member]
Assets [Abstract]
Fair value of assets	[5]	11	16
Liabilities [Abstract]
Fair value of liabilities	[5]	2	9
Basis Swaps [Member]
Liabilities [Abstract]
Fair value of liabilities	[5]	1	1
Level 1 [Member] | Restricted Cash [Member]
Assets [Abstract]
Fair value of assets	[1]	174	185
Level 1 [Member] | Money Market Funds [Member]
Assets [Abstract]
Fair value of assets	[2]	8,624	9,133
Level 1 [Member] | Available-for-sale Investments [Member]
Assets [Abstract]
Fair value of assets	[3]	28	32
Level 1 [Member] | Interest Rate Swaps [Member]
Assets [Abstract]
Fair value of assets	[4]		0
Level 1 [Member] | Foreign Currency Forwards [Member]
Assets [Abstract]
Fair value of assets	[5]	0	0
Liabilities [Abstract]
Fair value of liabilities	[5]	0	0
Level 1 [Member] | Basis Swaps [Member]
Liabilities [Abstract]
Fair value of liabilities	[5]	0	0
Level 2 [Member] | Restricted Cash [Member]
Assets [Abstract]
Fair value of assets	[1]	0	0
Level 2 [Member] | Money Market Funds [Member]
Assets [Abstract]
Fair value of assets	[2]	0	0
Level 2 [Member] | Available-for-sale Investments [Member]
Assets [Abstract]
Fair value of assets	[3]	0	0
Level 2 [Member] | Interest Rate Swaps [Member]
Assets [Abstract]
Fair value of assets	[4]		3
Level 2 [Member] | Foreign Currency Forwards [Member]
Assets [Abstract]
Fair value of assets	[5]	11	16
Liabilities [Abstract]
Fair value of liabilities	[5]	2	9
Level 2 [Member] | Basis Swaps [Member]
Liabilities [Abstract]
Fair value of liabilities	[5]	1	1
Level 3 [Member] | Restricted Cash [Member]
Assets [Abstract]
Fair value of assets	[1]	0	0
Level 3 [Member] | Money Market Funds [Member]
Assets [Abstract]
Fair value of assets	[2]	0	0
Level 3 [Member] | Available-for-sale Investments [Member]
Assets [Abstract]
Fair value of assets	[3]	0	0
Level 3 [Member] | Interest Rate Swaps [Member]
Assets [Abstract]
Fair value of assets	[4]		0
Level 3 [Member] | Foreign Currency Forwards [Member]
Assets [Abstract]
Fair value of assets	[5]	0	0
Liabilities [Abstract]
Fair value of liabilities	[5]	0	0
Level 3 [Member] | Basis Swaps [Member]
Liabilities [Abstract]
Fair value of liabilities	[5]	$ 0	$ 0

[1] Restricted cash consists of deposits restricted under agency agreements and cash restricted by law and other obligations.

[2] Money market funds are valued at the closing price reported by the fund sponsor.

[3] Fair values of quoted investments are based on current bid prices as of the balance sheet dates.

[4] The fair value of interest rate swaps is calculated by discounting the estimated future cash flows based on the applicable observable yield curves. See Note 7, Financial Instruments for additional information.

[5] The fair value of basis swaps and forward currency contracts is estimated by discounting the difference between the contractual forward price and the current available forward price for the residual maturity of the contract using observable market rates.