Shareholders' Equity (Accumulated other comprehensive income) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance	[1]	$ (13,903)	$ (9,894)	$ (17,416)
OCI before reclassifications	[1]	(51)	(4,878)	5,954
Amounts reclassified from AOCI	[1]	1,206	869	1,568
Net current period OCI	[1]	1,155	(4,009)	7,522
Balance	[1]	(12,748)	(13,903)	(9,894)
Defined benefit pension plans & other postretirement benefits:
Amortization of actuarial losses included in net periodic pension cost, net of tax of ($570), ($367), and ($849)		1,038	661	1,516
Amortization of actuarial losses included in net periodic pension cost, tax		(570)	(367)	(849)
Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance		53	150	214
OCI before reclassifications		(92)	(97)	(64)
Net current period OCI		(92)	(97)	(64)
Balance		(39)	53	150
Unrealized Gains and Losses on Certain Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance		(8)	(8)	$ (8)
OCI before reclassifications		8
Net current period OCI		$ 8
Balance			(8)	$ (8)
Unrealized Gains and Losses on Derivative Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance		$ (136)	(6)	86
OCI before reclassifications		(140)	(137)	(75)
Amounts reclassified from AOCI		79	7	(17)
Net current period OCI		(61)	(130)	(92)
Balance		(197)	(136)	(6)
Defined Benefit Pension Plans and Other Postretirement Benefits
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance		(13,812)	(10,030)	(17,708)
OCI before reclassifications		173	(4,644)	6,093
Amounts reclassified from AOCI	[2]	1,127	862	1,585
Net current period OCI		1,300	(3,782)	7,678
Balance		$ (12,512)	$ (13,812)	$ (10,030)

[1] Net of tax.

[2] Primarily relates to amortization of actuarial losses for the years ended December 31, 2015, 2014, and 2013 totaling $1,038, $661, and $1,516 (net of tax of ($570), ($367), and ($849)), respectively. These are included in the net periodic pension cost of which a portion is allocated to production as inventoried costs. See Note 14.