Note 16. Income Taxes consolidated income before loss (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
IRELAND
Operating Loss Carryforwards [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	$ (6)	$ 0	$ 0
UNITED STATES
Operating Loss Carryforwards [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	122	330	493
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	$ 945	$ 47	$ 451