Reorganization of Businesses - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) employee	Dec. 31, 2016 USD ($) employee	Dec. 31, 2015 USD ($) employee	Dec. 31, 2014 USD ($)
Restructuring Cost and Reserve [Line Items]
Maximum severance benefits salary period	6 months
Reorganization of business charges	$ 42	$ 140	$ 117
Net adjustment of accruals	(9)	(5)	(10)
Restructuring reserve	50	101	60	$ 57
Additional charges	51	125	84
Cash payments for exit costs	93	79	71
Continuing Operations
Restructuring Cost and Reserve [Line Items]
Net adjustment of accruals			(4)
Employee separation costs
Restructuring Cost and Reserve [Line Items]
Reorganization of business charges	43	120	74
Net adjustment of accruals	(9)	(4)	(10)
Restructuring reserve	41	94	51	57
Additional charges	43	120	74
Cash payments for exit costs	$ 87	$ 73	$ 70
Restructuring charges in the period for total employee severance (in number of employees) | employee	400	1,300	1,100
Restructuring charges in the period for direct employees' severance (in number of employees) | employee	100	400	200
Restructuring charges in the period for indirect employees' severance (in number of employees) | employee	300	900	900
Number of employees expected to be paid (in number of employees) | employee	100
Employee separation costs | Discontinued Operations
Restructuring Cost and Reserve [Line Items]
Net adjustment of accruals			$ (6)
Exit costs
Restructuring Cost and Reserve [Line Items]
Reorganization of business charges	$ 8	$ 5	10
Net adjustment of accruals	0	(1)	0
Restructuring reserve	9	7	9	$ 0
Additional charges	8	5	10
Cash payments for exit costs	6	6	1
Air Transportation Equipment | Asset Impairment Due Reorganization
Restructuring Cost and Reserve [Line Items]
Asset impairment charges		3	31
Building | Asset Impairment Due Reorganization
Restructuring Cost and Reserve [Line Items]
Asset impairment charges		17	6
Costs of sales
Restructuring Cost and Reserve [Line Items]
Reorganization of business charges	9	43	9
Other charges
Restructuring Cost and Reserve [Line Items]
Reorganization of business charges	$ 33	$ 97	$ 108