Retirement Plans Summary of Changes in Fair Value of Assets Measured Using Significant Unobservable Inputs (Level 3) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
U.S. Pension Plans
Retirement Plans [Line Items]
Fair value of plan assets at beginning of year	$ 2,606	$ 2,504
Fair value of plan assets at end of year	3,293	2,606
U.S. Pension Plans | Real Estate
Retirement Plans [Line Items]
Fair value of plan assets at beginning of year	323
Fair value of plan assets at end of year	346	323
Non-U.S. Pension
Retirement Plans [Line Items]
Fair value of plan assets at beginning of year	1,177	1,201
Fair value of plan assets at end of year	2,536	1,177
Non-U.S. Pension | Hedge Funds
Retirement Plans [Line Items]
Fair value of plan assets at beginning of year	172
Fair value of plan assets at end of year	169	172
Non-U.S. Pension | Real Estate
Retirement Plans [Line Items]
Fair value of plan assets at beginning of year	58
Fair value of plan assets at end of year	63	58
Fair Value, Inputs, Level 3 | U.S. Pension Plans
Retirement Plans [Line Items]
Fair value of plan assets at beginning of year	323	335
Additions net of redemptions	(6)	(59)
Realized gain	13	28
Unrealized gain (loss)	16	19
Fair value of plan assets at end of year	346	323
Fair Value, Inputs, Level 3 | U.S. Pension Plans | Hedge Funds
Retirement Plans [Line Items]
Fair value of plan assets at beginning of year	0	4
Additions net of redemptions	0	(3)
Realized gain	0	(1)
Unrealized gain (loss)	0	0
Fair value of plan assets at end of year	0	0
Fair Value, Inputs, Level 3 | U.S. Pension Plans | Real Estate
Retirement Plans [Line Items]
Fair value of plan assets at beginning of year	323	331
Additions net of redemptions	(6)	(56)
Realized gain	13	29
Unrealized gain (loss)	16	19
Fair value of plan assets at end of year	346	323
Fair Value, Inputs, Level 3 | Non-U.S. Pension
Retirement Plans [Line Items]
Fair value of plan assets at beginning of year	51	20
Additions net of redemptions		34
Unrealized gain (loss)	1	(3)
Fair value of plan assets at end of year	52	51
Fair Value, Inputs, Level 3 | Non-U.S. Pension | Hedge Funds
Retirement Plans [Line Items]
Fair value of plan assets at beginning of year	0	0
Additions net of redemptions		0
Unrealized gain (loss)	0	0
Fair value of plan assets at end of year	0	0
Fair Value, Inputs, Level 3 | Non-U.S. Pension | Real Estate
Retirement Plans [Line Items]
Fair value of plan assets at beginning of year	51	20
Additions net of redemptions		34
Unrealized gain (loss)	1	(3)
Fair value of plan assets at end of year	$ 52	$ 51