Accumulated Other Comprehensive Income AOCI by Component (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Balance		$ 42,649		$ 43,009
Balance		43,009		36,172
Equity Method Investee [Member]
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Balance		(3)		(3)
Other Comprehensive Income (Loss), before Reclassifications		1		0
Amounts reclassified from AOCI		(1)		0
Balance		(3)		(3)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Balance	[1]	133		234
Other Comprehensive Income (Loss), before Reclassifications	[1]	(126)		114
Amounts reclassified from AOCI	[1]	25		(2)	[2]
Balance	[1]	234		122
Accumulated Other Comprehensive Income (Loss) [Member]
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Balance		130		231
Other Comprehensive Income (Loss), before Reclassifications		(125)		114
Amounts reclassified from AOCI		24	[2]	(2)
Balance		$ 231		$ 119

[1] Amounts are net of tax. See Note 14 to the Consolidated Financial Statements for additional details.

[2] Amounts in parentheses indicate debits to the income statement.