Pension Plans, Retirement Benefits and Savings Plans (details) - Additional Pension Disclosures - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income:
Total other changes in benefit plan assets and benefit obligations recognized in other comprehensive income	$ (66)	$ 494	$ (647)
Pension Plans [Member]
Defined benefit plan disclosure
Total accumulated benefit obligation	3,370	3,510
Aggregate projected benefit obligation for pension plans with an accumulated benefit obligation in excess of plan assets	3,470	3,530
Aggregate accumulated benefit obligation for pension plans with an accumulated benefit obligation in excess of plan assets	3,360	3,430
Fair value of plan assets for pension plans with an accumulated benefit obligation in excess of plan assets	3,230	3,270
Components of net periodic benefit cost
Service cost	131	110	118
Interest cost on benefit obligation	144	150	132
Expected return on plan assets	(230)	(218)	(208)
Net periodic benefit cost, curtailment		(1)
Net periodic benefit cost, settlement		2
Net periodic benefit cost, amortization of unrecognized prior service benefit	(1)
Net periodic benefit cost, amortization of unrecognized net actuarial loss (gain)	96	65	107
Net periodic benefit cost	140	108	149
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income:
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, prior service benefit		(8)
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, net actuarial loss (gain)	43	516	(518)
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, curtailment		(2)
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, settlement		(2)
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, amortization of prior service benefit	1
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, amortization of net actuarial gain (loss)	(96)	(65)	(107)
Total other changes in benefit plan assets and benefit obligations recognized in other comprehensive income	(52)	439	(625)
Total other changes recognized in net periodic benefit cost and other comprehensive income	88	547	(476)
Estimated net actuarial loss that will be amortized from other comprehensive income into net periodic benefit cost over the next fiscal year	66
Estimated prior service benefit to be amortized over the next fiscal year	1
Qualified Domestic Pension Plan [Member]
Defined benefit plan disclosure
Total accumulated benefit obligation	3,150	3,290
Required contributions made	0	0	0
Required contributions during next fiscal year	0
Components of net periodic benefit cost
Service cost	124	104
Interest cost on benefit obligation	135	140
Nonqualified and Foreign Pension Plans [Member]
Defined benefit plan disclosure
Total accumulated benefit obligation	220	220
Components of net periodic benefit cost
Service cost	7	6
Interest cost on benefit obligation	9	10
Foreign Pension Plan [Member]
Defined benefit plan disclosure
Required contributions during next fiscal year	0
Postretirement Benefit Plans [Member]
Components of net periodic benefit cost
Interest cost on benefit obligation	10	10	9
Expected return on plan assets			(1)
Net periodic benefit cost, amortization of unrecognized prior service benefit	(3)	(2)	(2)
Net periodic benefit cost, amortization of unrecognized net actuarial loss (gain)	1	(3)
Net periodic benefit cost	8	5	6
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income:
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, prior service benefit	(11)
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, net actuarial loss (gain)	(3)	50	(24)
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, amortization of prior service benefit	3	2	2
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, amortization of net actuarial gain (loss)	(1)	3
Total other changes in benefit plan assets and benefit obligations recognized in other comprehensive income	(12)	55	(22)
Total other changes recognized in net periodic benefit cost and other comprehensive income	(4)	$ 60	$ (16)
Estimated prior service benefit to be amortized over the next fiscal year	3
Postretirement Benefit Plans [Member] | Maxiumum [Member]
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income:
Estimated net actuarial loss that will be amortized from other comprehensive income into net periodic benefit cost over the next fiscal year	$ 1