Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Maximum annual medical cost inflation after retirement for Company's share of retiree medical benefits cost for non Medicare-eligible retirees (as a percent)	5.00%
Items not yet recognized as a component of net periodic cost:
Deferred income tax				$ (487)	$ (90)
Unrecognized pension and other postretirement benefit cost				1,419	1,315
Pension benefits
Components of net periodic cost
Fair value of plan assets	$ 5,353	$ 5,783	$ 5,783	5,650	5,353
Less: Benefit obligation	6,130	6,493	6,493	6,591	6,130
Funded status				(941)	(777)
Items not yet recognized as a component of net periodic cost:
Net actuarial loss (gain)				2,807	2,710
Prior service credit				(310)	(365)
Unrecognized pension and other postretirement benefit cost, pre-tax	2,345	2,345		2,497	2,345
Deferred income tax				(874)	(821)
Unrecognized pension and other postretirement benefit cost				1,623	1,524
Increase (decrease) in defined benefit net actuarial loss arising during the period	$ 97
Percentage of underfunded status relating to the primary employee plans	81.00%
Change in items not yet recognized as a component of defined benefit plans, net periodic cost
Items not yet recognized as a component of net periodic cost – December 31, 2015	$ 2,345
Net actuarial loss (gain) arising during the period	294
Net actuarial (loss) gain amortized to net periodic benefit cost	(201)
Prior service credit arising during the period	0
Prior service credit amortized to net periodic benefit cost	56
Translation adjustment and other	3
Items not yet recognized as a component of net periodic cost – December 31, 2016	2,497	2,345
Estimates of the net actuarial loss (gain) and prior service credit expected to be recognized as a component of net periodic benefit cost during 2015
Net actuarial loss (gain)	189
Prior service credit	(56)
Accumulated benefit obligation (ABO)				6,520	6,050
Company's Pension Plans with an ABO in excess of plan assets
Company's pension plans with ABO in excess of plan assets, aggregate projected benefit obligation				6,240	5,810
Company's pension plans with ABO in excess of plan assets, aggregate accumulated benefit obligation				6,180	5,740
Company's pension plans with ABO in excess of plan assets, aggregate fair value of plan assets				5,300	5,020
Defined benefit plans' accrued benefit costs related to certain unfunded and non-qualified plans				$ 141	$ 143
Change in benefit obligation
Benefit obligation, beginning of year	6,130	6,493
Service cost	113	114	96
Interest cost	286	258	262
Participant contributions	1	0
Actuarial loss (gain)	387	(225)
Benefits paid	(301)	(443)
Plan amendments	0	0
Translation adjustment and other	(25)	(67)
Benefit obligation, end of year	6,591	6,130	6,493
Components of net periodic cost
Service cost	113	114	96
Interest cost	286	258	262
Expected return on plan assets	(398)	(424)	(398)
Amortization of:
Prior service credit	(56)	(56)	(58)
Net actuarial loss (gain)	174	190	127
Settlement loss	27	31	54
Net periodic cost (credit)	$ 146	$ 113	$ 83
Weighted average assumptions used to determine net pension cost and net postretirement benefit cost
Discount rate	4.83%	4.10%	5.00%
Rate of increase in compensation levels	3.20%	3.50%	3.50%
Expected long-term rate of return on plan assets	7.30%	7.33%	7.36%
Weighted average assumptions used to determine benefit obligations
Discount rate				4.15%	4.83%
Rate of increase in compensation levels				3.20%	3.20%
Pension plan assets
Fair value of plan assets, beginning of year	$ 5,353	$ 5,783
Actual return on plan assets	491	(43)
Employer contribution	131	125
Benefits paid	(301)	(443)
Translation adjustment and other	(24)	(69)
Fair value of plan assets, end of year	5,650	5,353	$ 5,783
Postretirement benefits
Components of net periodic cost
Fair value of plan assets	0	0		$ 0	$ 0
Less: Benefit obligation	405	575	575	373	405
Funded status				(373)	(405)
Items not yet recognized as a component of net periodic cost:
Net actuarial loss (gain)				(251)	(263)
Prior service credit				(62)	(61)
Unrecognized pension and other postretirement benefit cost, pre-tax	(324)	(324)		(313)	(324)
Deferred income tax				109	115
Unrecognized pension and other postretirement benefit cost				$ (204)	$ (209)
Increase (decrease) in defined benefit net actuarial loss arising during the period	(12)
Change in items not yet recognized as a component of defined benefit plans, net periodic cost
Items not yet recognized as a component of net periodic cost – December 31, 2015	(324)
Net actuarial loss (gain) arising during the period	(14)
Net actuarial (loss) gain amortized to net periodic benefit cost	24
Prior service credit arising during the period	(22)
Prior service credit amortized to net periodic benefit cost	21
Translation adjustment and other	2
Items not yet recognized as a component of net periodic cost – December 31, 2016	(313)	(324)
Estimates of the net actuarial loss (gain) and prior service credit expected to be recognized as a component of net periodic benefit cost during 2015
Net actuarial loss (gain)	(24)
Prior service credit	(24)
Change in benefit obligation
Benefit obligation, beginning of year	405	575
Service cost	9	12	10
Interest cost	17	23	23
Participant contributions	16	19
Actuarial loss (gain)	(14)	(158)
Benefits paid	(41)	(54)
Plan amendments	(22)	0
Translation adjustment and other	3	(12)
Benefit obligation, end of year	373	405	575
Components of net periodic cost
Service cost	9	12	10
Interest cost	17	23	23
Expected return on plan assets	0	0	0
Amortization of:
Prior service credit	(21)	(22)	(23)
Net actuarial loss (gain)	(24)	(9)	(22)
Settlement loss	0	0	0
Net periodic cost (credit)	$ (19)	$ 4	$ (12)
Weighted average assumptions used to determine net pension cost and net postretirement benefit cost
Discount rate	4.59%	3.97%	5.11%
Weighted average assumptions used to determine benefit obligations
Discount rate				4.07%	4.56%
Defined benefit plan, assumed health care cost trend rates
Defined Benefit plan, Weighted average health care cost trend rate	6.30%
Defined Benefit plan, ultimate health care cost trend rate in 2038 and thereafter	4.50%
Increase in the total of service and interest cost components of net periodic benefit cost due to one percentage-point increase in assumed health care cost trend rates	$ 2
Increase in APBO due to one percentage-point increase in assumed health care cost trend rates	24
Decrease in APBO due to one percentage-point decrease in assumed health care cost trend rates	2
Decrease in the total of service and interest cost components of net periodic benefit cost due to one percentage-point decrease in assumed health care cost trend rates	21
Pension plan assets
Fair value of plan assets, beginning of year	0
Employer contribution	25	$ 35
Benefits paid	(41)	(54)
Fair value of plan assets, end of year	$ 0	$ 0