Fair Value Measurements (Details) - Recurring - USD ($) $ in Millions	Feb. 28, 2017	Aug. 31, 2016
Restricted cash
Assets [Abstract]
Fair value of assets	$ 170	$ 185
Money market funds
Assets [Abstract]
Fair value of assets	10,106	9,133
Available-for-sale investments
Assets [Abstract]
Fair value of assets	28	32
Interest rate swaps
Assets [Abstract]
Fair value of assets		3
Liabilities [Abstract]
Fair value of liabilities	1
Foreign currency forwards
Assets [Abstract]
Fair value of assets	2	16
Liabilities [Abstract]
Fair value of liabilities	11
Basis swaps
Liabilities [Abstract]
Fair value of liabilities	1	1
Level 1 | Restricted cash
Assets [Abstract]
Fair value of assets	170	185
Level 1 | Money market funds
Assets [Abstract]
Fair value of assets	10,106	9,133
Level 1 | Available-for-sale investments
Assets [Abstract]
Fair value of assets	28	32
Level 1 | Interest rate swaps
Assets [Abstract]
Fair value of assets		0
Liabilities [Abstract]
Fair value of liabilities	0
Level 1 | Foreign currency forwards
Assets [Abstract]
Fair value of assets	0	0
Liabilities [Abstract]
Fair value of liabilities	0
Level 1 | Basis swaps
Liabilities [Abstract]
Fair value of liabilities	0	0
Level 2 | Restricted cash
Assets [Abstract]
Fair value of assets	0	0
Level 2 | Money market funds
Assets [Abstract]
Fair value of assets	0	0
Level 2 | Available-for-sale investments
Assets [Abstract]
Fair value of assets	0	0
Level 2 | Interest rate swaps
Assets [Abstract]
Fair value of assets		3
Liabilities [Abstract]
Fair value of liabilities	1
Level 2 | Foreign currency forwards
Assets [Abstract]
Fair value of assets	2	16
Liabilities [Abstract]
Fair value of liabilities	11
Level 2 | Basis swaps
Liabilities [Abstract]
Fair value of liabilities	1	1
Level 3 | Restricted cash
Assets [Abstract]
Fair value of assets	0	0
Level 3 | Money market funds
Assets [Abstract]
Fair value of assets	0	0
Level 3 | Available-for-sale investments
Assets [Abstract]
Fair value of assets	0	0
Level 3 | Interest rate swaps
Assets [Abstract]
Fair value of assets		0
Liabilities [Abstract]
Fair value of liabilities	0
Level 3 | Foreign currency forwards
Assets [Abstract]
Fair value of assets		0
Liabilities [Abstract]
Fair value of liabilities	0
Level 3 | Basis swaps
Liabilities [Abstract]
Fair value of liabilities	$ 0	$ 0