Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
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				$ (90)	$ (715)
Unrecognized pension and other postretirement benefit cost				1,315	1,363
Pension benefits
Components of net periodic cost
Fair value of plan assets	$ 5,783	$ 5,602	$ 5,602	5,353	5,783
Less: Benefit obligation	6,493	5,297	5,297	6,130	6,493
Funded status				(777)	(710)
Items not yet recognized as a component of net periodic cost:
Net actuarial loss (gain)				2,710	2,707
Prior service credit				(365)	(422)
Unrecognized pension and other postretirement benefit cost, pre-tax	2,285	2,285		2,345	2,285
Deferred income tax				(821)	(800)
Unrecognized pension and other postretirement benefit cost				1,524	1,485
Increase (decrease) in defined benefit net actuarial loss arising during the period	$ 3
Percentage of underfunded status relating to the primary employee plans	79.00%
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, 2014	$ 2,285
Net actuarial loss (gain) arising during the period	242
Net actuarial (loss) gain amortized to net periodic benefit cost	221
Prior service credit arising during the period	0
Prior service credit amortized to net periodic benefit cost	(56)
Translation adjustment and other	(17)
Items not yet recognized as a component of net periodic cost – December 31, 2015	2,345	2,285
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)	174
Prior service credit	(56)
Accumulated benefit obligation (ABO)				6,050	6,420
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				5,810	6,120
Company's pension plans with ABO in excess of plan assets, aggregate accumulated benefit obligation				5,740	6,060
Company's pension plans with ABO in excess of plan assets, aggregate fair value of plan assets				5,020	5,380
Defined benefit plans' accrued benefit costs related to certain unfunded and non-qualified plans				$ 143	$ 147
Change in benefit obligation
Benefit obligation, beginning of year	6,493	5,297
Service cost	114	96	140
Interest cost	258	262	265
Participant contributions	0	1
Actuarial (gain) loss	(225)	1,243
Benefits paid	(443)	(368)
Plan amendments	0	0
Translation adjustment and other	(67)	(38)
Curtailment gain	0	0
Benefit obligation, end of year	6,130	6,493	5,297
Components of net periodic cost
Service cost	114	96	140
Interest cost	258	262	265
Expected return on plan assets	(424)	(398)	(394)
Amortization of:
Prior service credit	(56)	(58)	(28)
Net actuarial loss (gain)	190	127	235
Settlement loss	31	54	277
Curtailment gain	0	0	0
Net periodic cost (credit)	$ 113	$ 83	$ 495
Weighted average assumptions used to determine net pension cost and net postretirement benefit cost
Discount rate (as a percent)	4.10%	5.00%	4.60%
Rate of increase in compensation levels (as a percent)	3.50%	3.50%	3.50%
Expected long-term rate of return on plan assets (as a percent)	7.33%	7.36%	7.75%
Weighted average assumptions used to determine benefit obligations
Discount rate (as a percent)				4.83%	4.10%
Rate of increase in compensation levels (as a percent)				3.20%	3.50%
Pension plan assets
Fair value of plan assets, beginning of year	$ 5,783	$ 5,602
Actual return on plan assets	(43)	540
Employer contribution	125	49
Benefits paid	(443)	(368)
Translation adjustment and other	(69)	(40)
Fair value of plan assets, end of year	5,353	5,783	$ 5,602
Postretirement benefits
Components of net periodic cost
Fair value of plan assets	0	0		$ 0	$ 0
Less: Benefit obligation	575	482	482	405	575
Funded status				(405)	(575)
Items not yet recognized as a component of net periodic cost:
Net actuarial loss (gain)				(263)	(111)
Prior service credit				(61)	(83)
Unrecognized pension and other postretirement benefit cost, pre-tax	(194)	(194)		(324)	(194)
Deferred income tax				115	72
Unrecognized pension and other postretirement benefit cost				$ (209)	$ (122)
Increase (decrease) in defined benefit net actuarial loss arising during the period	152
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, 2014	(194)
Net actuarial loss (gain) arising during the period	(158)
Net actuarial (loss) gain amortized to net periodic benefit cost	(9)
Prior service credit arising during the period	0
Prior service credit amortized to net periodic benefit cost	(22)
Translation adjustment and other	(3)
Items not yet recognized as a component of net periodic cost – December 31, 2015	(324)	(194)
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)	(32)
Prior service credit	(21)
Change in benefit obligation
Benefit obligation, beginning of year	575	482
Service cost	12	10	12
Interest cost	23	23	28
Participant contributions	19	19
Actuarial (gain) loss	(158)	103
Benefits paid	(54)	(57)
Plan amendments	0	0
Translation adjustment and other	(12)	(5)
Curtailment gain	0	0
Benefit obligation, end of year	405	575	482
Components of net periodic cost
Service cost	12	10	12
Interest cost	23	23	28
Expected return on plan assets	0	0	0
Amortization of:
Prior service credit	(22)	(23)	(23)
Net actuarial loss (gain)	(9)	(22)	(16)
Settlement loss	0	0	0
Curtailment gain	0	0	(181)
Net periodic cost (credit)	$ 4	$ (12)	$ (180)
Weighted average assumptions used to determine net pension cost and net postretirement benefit cost
Discount rate (as a percent)	3.97%	5.11%	3.75%
Weighted average assumptions used to determine benefit obligations
Discount rate (as a percent)				4.56%	4.15%
Defined benefit plan, assumed health care cost trend rates
Defined Benefit plan, Weighted average health care cost trend rate (as a percent)	6.30%
Defined Benefit plan, ultimate health care cost trend rate in 2038 and thereafter (as a percent)	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	$ 3
Increase in APBO due to one percentage-point increase in assumed health care cost trend rates	20
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	17
Pension plan assets
Fair value of plan assets, beginning of year	0
Employer contribution	35	$ 38
Benefits paid	(54)	(57)
Fair value of plan assets, end of year	$ 0	$ 0