Restructuring Costs (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restructuring Cost [Abstract]
Restructuring costs	$ 395	$ 679	$ 1,019	$ 898	$ 432
Employee separation costs			297	641
Employee Separation Activity
Liability balance at beginning of period			483	182
Employee separation costs			297	641
Reduction in liability (payments and other adjustments)			633	340
Liability balance at end of period	147	$ 483	147	483	182
Other restructuring costs
Restructuring Cost [Abstract]
Restructuring costs			262	48	0
Voluntary retirement enhancement program
Restructuring Cost [Abstract]
Curtailment expense				(82)
Employee separation costs			100	379
Employee Separation Activity
Employee separation costs			100	379
Facility closures and consolidations
Restructuring Cost [Abstract]
Restructuring costs			181	108
Other operating income (expense) | Employee separation
Restructuring Cost [Abstract]
Restructuring costs			297	641	382
Other operating income (expense) | Contract termination
Restructuring Cost [Abstract]
Restructuring costs			62	0	0
Other operating income (expense) | Long-lived asset impairments
Restructuring Cost [Abstract]
Restructuring costs			391	127	48
Other operating income (expense) | Defined benefit retirement plan curtailment losses
Restructuring Cost [Abstract]
Restructuring costs			7	$ 82	$ 2
Discontinue production on-highway vocational trucks
Restructuring Cost [Abstract]
Restructuring costs			104
Estimated restructuring costs	110		110
Second half of 2016 announcement
Restructuring Cost [Abstract]
Restructuring costs			369
Estimated restructuring costs	$ 385		385
Second half of 2016 announcement | Other restructuring costs
Restructuring Cost [Abstract]
Restructuring costs			4
Second half of 2016 announcement | Employee separation
Restructuring Cost [Abstract]
Employee separation costs			120
Employee Separation Activity
Employee separation costs			120
Second half of 2016 announcement | Inventory write-downs
Restructuring Cost [Abstract]
Restructuring costs			81
Second half of 2016 announcement | Long-lived asset impairments
Restructuring Cost [Abstract]
Restructuring costs			$ 164