Income Taxes Components of Provision for Income Taxes on Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Components of Income Tax [Line Items]
Income from Continuing Operations before Income Taxes, Domestic		$ 868	$ 943	$ 418
Current
Federal		(225)	169	(688)
State		(6)	5	(33)
Foreign		373	788	550
Total		142	962	(171)
Deferred
Federal		593	(321)	410
State		41	(15)	(2)
Foreign		(71)	(429)	(166)
Total		563	(765)	242
Income tax provision		705	197	71
Income from Continuing Operations before Income Taxes, Foreign		1,690	119	513
Income Taxes Paid		1,756	1,388	1,163
Taxes Payable, Current	$ 625	625	1,505
Undistributed Earnings of Foreign Subsidiaries	16,000	16,000
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	$ 53	$ 34	$ (29)	(7)
Global Workplace Solutions
Deferred
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount				$ 680