Income Taxes - Tax Credit Carryforwards (Details 7) $ in Millions	Aug. 31, 2017 USD ($)
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 649
2018 - 2022
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	110
2023 - 2027
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	136
2028 - 2032
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	140
2033 - 2037
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	206
Indefinite
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	57
U.S. Federal
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	416
U.S. Federal | 2018 - 2022
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	48
U.S. Federal | 2023 - 2027
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	99
U.S. Federal | 2028 - 2032
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	64
U.S. Federal | 2033 - 2037
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	205
U.S. Federal | Indefinite
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	0
State
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	233
State | 2018 - 2022
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	62
State | 2023 - 2027
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	37
State | 2028 - 2032
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	76
State | 2033 - 2037
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	1
State | Indefinite
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 57