Note 16. Income Taxes Examination Year (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount		$ 136	$ 336
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount		0	15
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	$ (67)	(92)	(13)
Effective Income Tax Rate Reconciliation, Deduction, Amount	21
Effective Income Tax Rate Reconciliation, Tax Credit, Amount		7	6
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount			75
Unrecognized Tax Benefits, Period Increase (Decrease)		471
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount		14	(13)
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount		7	(5)
Income Tax Expense (Benefit)	99	$ 1,839	$ 418
IRELAND
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	133
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	(10)
Effective Income Tax Rate Reconciliation, Deduction, Amount	28
Effective Income Tax Rate Reconciliation, Tax Credit, Amount	13
Effective Income Tax Rate Reconciliation, Equity in Earnings (Losses) of Unconsolidated Subsidiary, Amount	(19)
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount	30
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Amount	11
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	10
Unrecognized Tax Benefits, Period Increase (Decrease)	50
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	21
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	3
Income Tax Expense (Benefit)	$ 99
Secretariat of the Federal Revenue Bureau of Brazil [Member] | Tax Year 2012 [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Year under Examination	2012
State Administration of Taxation, China [Member] | Tax Year 2011 [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Year under Examination	2011
MTS CZECH REPUBLIC [Member] | Tax Year 2008 [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Year under Examination	2008
Ministry of the Economy, Finance and Industry, France [Member] | Tax Year 2013 [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Year under Examination	2013
Federal Ministry of Finance, Germany [Member] | Tax Year 2013 [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Year under Examination	2013
Inland Revenue, Hong Kong [Member] | Tax Year 2011 [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Year under Examination	2011
National Tax Agency, Japan [Member] | Tax Year 2012 [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Year under Examination	2012
Luxembourg Inland Revenue [Member] | Tax Year 2008 [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Year under Examination	2012
Mexican Tax Authority [Member] | Tax Year 2012 [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Year under Examination	2012
KDPW_CCP [Member] | Tax Year 2008 [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Year under Examination	2008
HSBC-X UNITED KINGDOM [Member] | Tax Year 2011 [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Year under Examination	2011
State and Local Jurisdiction [Member] | Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Year under Examination	2017