Income Tax (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits
Balance at January 1,	$ 1,111	$ 1,102	$ 1,146
Additions for tax positions of prior years (1)	6	269	70
Reductions for tax positions of prior years (2)	(493)	(195)	(101)
Additions for tax positions of current year (1)	13	226	33
Reductions for tax positions of current year	0	(3)	(3)
Settlements with tax authorities (3)	(381)	(288)	(43)
Balance at December 31,	256	1,111	1,102
Unrecognized tax benefits that, if recognized, would impact the effective rate	194	1,046	$ 1,073
Current Income Tax Payable
Reconciliation of Unrecognized Tax Benefits
Settlements with tax authorities (3)	$ (377)	$ (284)