Equity and Noncontrolling Interests - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020		Jun. 30, 2019		Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Foreign currency translation adjustments
Balance at beginning of period		$ (1,005)	$ (952)	$ (785)		$ (939)
Aggregate adjustment for the period		72	(90)	(148)		(103)
Aggregate adjustment for period, tax effect		0	0	0		0
Balance at end of period		(933)	(563)	(933)		(563)
Realized and unrealized gains (losses) on derivatives
Balance at beginning of period		(7)	2	(2)		(13)
Current period change in fair value		4	(4)	1		4
Current period change in fair value, Tax		1	(3)	0		1
Reclassification to income	[1]	2	(1)	0		6
Reclassifcation to income, tax effect		0	0	0	[1]	3	[1]
Balance at end of period		(1)	1	(1)		1
Realized and unrealized gains (losses) on marketable securities
Balance at beginning of period				0		8
Adoption of ASU		17,805	20,363	17,805		20,363		$ 18,084	$ 19,766	$ 20,036	$ 21,164
Balance at end of period		0	0	0		0
Pension and postretirement plans
Balance at beginning of period		(9)	(2)	(8)		(2)
Reclassification to income		0	0	(1)		0
Reclassification to income, tax effect		0	0	0		0
Balance at end of period		(9)	(2)	(9)		(2)
Accumulated other comprehensive loss		(943)	(564)	(943)		(564)			(795)
Adoption of ASU 2016-01
Realized and unrealized gains (losses) on marketable securities
Balance at beginning of period				0	[2]	8
Retained Earnings
Realized and unrealized gains (losses) on marketable securities
Adoption of ASU		2,955	6,366	2,955		6,366		3,332	4,827	6,416	6,604
AOCI Attributable to Parent [Member]
Realized and unrealized gains (losses) on marketable securities
Adoption of ASU		(943)	(564)	(943)		(564)		$ (1,021)	$ (795)	$ (952)	$ (946)
AOCI Attributable to Parent [Member] | Adoption of ASU 2016-01
Realized and unrealized gains (losses) on marketable securities
Balance at beginning of period	[2]					(8)
Power Solutions
Realized and unrealized gains (losses) on derivatives
Reclassification to income		0	(4)	0		(4)
Pension and postretirement plans
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax		0	479	0		479
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax		$ 0	$ 1	$ 0		$ 1

[1] Refer to Note 16, "Derivative Instruments and Hedging Activities," of the notes to consolidated financial statements for disclosure of the line items in the consolidated statements of income affected by reclassifications from AOCI into income related to derivatives.

[2] During the quarter ended December 31, 2018, the Company adopted ASU 2016-01, "Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities." As a result, the Company reclassified $8 million of unrealized gains on marketable securities to retained earnings as of October 1, 2018.