Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Benefit Plans
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	$ (715,000,000)	$ (635,000,000)
Unrecognized pension and other postretirement benefit cost	1,363,000,000	638,000,000
Pension benefits
Components of net periodic cost
Fair value of plan assets	5,783,000,000	5,602,000,000	5,398,000,000
Less: Benefit obligation	6,493,000,000	5,297,000,000	6,727,000,000
Funded status	(710,000,000)	305,000,000
Items not yet recognized as a component of net periodic cost
Net actuarial loss (gain)	2,707,000,000	1,794,000,000
Prior service credit	(422,000,000)	(480,000,000)
Unrecognized pension and other postretirement benefit cost, pre-tax	2,285,000,000	1,314,000,000
Deferred income tax	(800,000,000)	(460,000,000)
Unrecognized pension and other postretirement benefit cost	1,485,000,000	854,000,000
Increase (decrease) in defined benefit net actuarial loss arising during the period	913,000,000
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, at the beginning of the period	1,314,000,000
Net actuarial loss arising during the period	1,101,000,000
Net actuarial (loss) gain amortized to net periodic benefit cost	(181,000,000)
Prior service credit amortized to net periodic benefit cost	58,000,000
Translation adjustment and other	(7,000,000)
Items not yet recognized as a component of net periodic cost, at the end of the period	2,285,000,000	1,314,000,000
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)	190,000,000
Prior service credit	(56,000,000)
Accumulated benefit obligation (ABO)	6,420,000,000	5,230,000,000
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	6,120,000,000	146,000,000
Company's pension plans with ABO in excess of plan assets, aggregate accumulated benefit obligation	6,060,000,000	145,000,000
Company's pension plans with ABO in excess of plan assets, aggregate fair value of plan assets	5,380,000,000	0
Defined benefit plans' accrued benefit costs related to certain unfunded and non-qualified plans	147,000,000	146,000,000
Change in benefit obligation
Benefit obligation, beginning of year	5,297,000,000	6,727,000,000
Service cost	96,000,000	140,000,000	152,000,000
Interest cost	262,000,000	265,000,000	298,000,000
Participant contributions	1,000,000	1,000,000
Actuarial loss (gain)	1,243,000,000	(406,000,000)
Benefits paid	(368,000,000)	(892,000,000)
Plan amendments		(506,000,000)
Translation adjustment and other	(38,000,000)	(31,000,000)
Curtailment gain		(1,000,000)
Benefit obligation, end of year	6,493,000,000	5,297,000,000	6,727,000,000
Components of net periodic cost
Service cost	96,000,000	140,000,000	152,000,000
Interest cost	262,000,000	265,000,000	298,000,000
Expected return on plan assets	(398,000,000)	(394,000,000)	(393,000,000)
Amortization of prior service credit	(58,000,000)	(28,000,000)	(2,000,000)
Amortization of net actuarial loss (gain)	127,000,000	235,000,000	178,000,000
Settlement loss	54,000,000	277,000,000	33,000,000
Net periodic cost (credit)	83,000,000	495,000,000	266,000,000
Weighted average assumptions used to determine net pension cost and net postretirement benefit cost
Discount rate (as a percent)	5.00%	4.60%	5.25%
Rate of increase in compensation levels	3.50%	3.50%	4.50%
Expected long-term rate of return on plan assets (as a percent)	7.36%	7.75%	8.50%
Weighted average assumptions used to determine benefit obligations
Discount rate (as a percent)	4.10%	5.00%
Rate of increase in compensation levels	3.50%	3.50%
Pension plan assets
Fair value of plan assets, beginning of year	5,602,000,000	5,398,000,000
Actual return on plan assets	540,000,000	566,000,000
Employer contribution	49,000,000	561,000,000
Benefits paid	(368,000,000)	(892,000,000)
Translation adjustment and other	(40,000,000)	(31,000,000)
Fair value of plan assets, end of year	5,783,000,000	5,602,000,000	5,398,000,000
Postretirement benefits
Components of net periodic cost
Less: Benefit obligation	575,000,000	482,000,000	803,000,000
Funded status	(575,000,000)	(482,000,000)
Items not yet recognized as a component of net periodic cost
Net actuarial loss (gain)	(111,000,000)	(236,000,000)
Prior service credit	(83,000,000)	(106,000,000)
Unrecognized pension and other postretirement benefit cost, pre-tax	(194,000,000)	(342,000,000)
Deferred income tax	72,000,000	126,000,000
Unrecognized pension and other postretirement benefit cost	(122,000,000)	(216,000,000)
Increase (decrease) in defined benefit net actuarial loss arising during the period	(125,000,000)
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, at the beginning of the period	(342,000,000)
Net actuarial loss arising during the period	103,000,000
Net actuarial (loss) gain amortized to net periodic benefit cost	22,000,000
Prior service credit amortized to net periodic benefit cost	23,000,000
Items not yet recognized as a component of net periodic cost, at the end of the period	(194,000,000)	(342,000,000)
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)	(9,000,000)
Prior service credit	(22,000,000)
Change in benefit obligation
Benefit obligation, beginning of year	482,000,000	803,000,000
Service cost	10,000,000	12,000,000	13,000,000
Interest cost	23,000,000	28,000,000	36,000,000
Participant contributions	19,000,000	18,000,000
Actuarial loss (gain)	103,000,000	(32,000,000)
Benefits paid	(57,000,000)	(57,000,000)
Translation adjustment and other	(5,000,000)	(5,000,000)
Curtailment gain		(285,000,000)
Benefit obligation, end of year	575,000,000	482,000,000	803,000,000
Components of net periodic cost
Service cost	10,000,000	12,000,000	13,000,000
Interest cost	23,000,000	28,000,000	36,000,000
Amortization of prior service credit	(23,000,000)	(23,000,000)	(23,000,000)
Amortization of net actuarial loss (gain)	(22,000,000)	(16,000,000)	(20,000,000)
Curtailment gain		(181,000,000)
Net periodic cost (credit)	(12,000,000)	(180,000,000)	6,000,000
Weighted average assumptions used to determine net pension cost and net postretirement benefit cost
Discount rate (as a percent)	5.11%	3.75%	5.25%
Weighted average assumptions used to determine benefit obligations
Discount rate (as a percent)	4.15%	4.85%
Defined benefit plan, assumed health care cost trend rates
Defined Benefit plan, Weighted average health care cost trend rate (as a percent)	6.80%
Defined Benefit plan, ultimate health care cost trend rate in 2024 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	2,000,000
Increase in APBO due to one percentage-point increase in assumed health care cost trend rates	25,000,000
Decrease in APBO due to one percentage-point decrease in assumed health care cost trend rates	2,000,000
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	24,000,000
Pension plan assets
Employer contribution	38,000,000	39,000,000
Benefits paid	$ (57,000,000)	$ (57,000,000)