Acquisitions, Goodwill and Intangible Assets - Goodwill (Details) - USD ($)	3 Months Ended
	Dec. 31, 2017	Sep. 30, 2017
Goodwill
Balance	$ 9,158,000,000
Acquisition adjustment	41,000,000
Foreign currency translation adjustments	7,000,000
Balance	9,206,000,000	$ 9,158,000,000
Impairment loss on goodwill		0
Interior Systems
Goodwill
Balance	7,223,000,000
Acquisition adjustment	(344,000,000)
Foreign currency translation adjustments	7,000,000
Balance	6,886,000,000	7,223,000,000
Commercial Systems
Goodwill
Balance	325,000,000
Acquisition adjustment	0
Foreign currency translation adjustments	0
Balance	325,000,000	325,000,000
Government Systems
Goodwill
Balance	506,000,000
Acquisition adjustment	385,000,000
Foreign currency translation adjustments	0
Balance	891,000,000	506,000,000
Information Management Services
Goodwill
Balance	1,104,000,000
Acquisition adjustment	0
Foreign currency translation adjustments	0
Balance	$ 1,104,000,000	$ 1,104,000,000