Accumulated Other Comprehensive Income (Details 1) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Other operating expenses	$ (770)	$ (739)	$ (684)	$ (940)	$ (803)	$ (651)	$ (657)	$ (650)	$ (3,133)	$ (2,761)	$ (2,579)
Interest expense - other									(1,116)	(1,005)	(973)
Total before taxes									1,512	1,426	1,078
Income taxes (benefits)	13	(133)	(121)	(249)	(1,232)	(202)	(132)	(149)	(490)	(1,715)	(527)
NET INCOME (LOSS) ATTRIBUTABLE TO COMMON STOCKHOLDERS	$ 128	$ (512)	$ 134	$ 1,213	$ (2,499)	$ 396	$ 174	$ 205	981	(1,724)	(6,177)
Reclassifications from AOCI | Gains & losses on cash flow hedges
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Total before taxes									8	10	8
Income taxes (benefits)									(2)	(4)	(3)
NET INCOME (LOSS) ATTRIBUTABLE TO COMMON STOCKHOLDERS									6	6	5
Reclassifications from AOCI | Gains & losses on cash flow hedges | Commodity contracts
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Other operating expenses									1	2	0
Reclassifications from AOCI | Gains & losses on cash flow hedges | Long-term debt
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Interest expense - other									7	8	8
Reclassifications from AOCI | Unrealized gains on AFS securities
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Investment income									(1)	(40)	(32)
Reclassifications from AOCI | Defined benefit pension and OPEB plans
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Prior-service costs									(74)	(74)	(72)
Income taxes (benefits)									19	28	27
NET INCOME (LOSS) ATTRIBUTABLE TO COMMON STOCKHOLDERS									$ (55)	$ (46)	$ (45)