Income Taxes Income Taxes (Schedule of Effective Tax Rate Reconciliation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Income tax provision computed at US federal statutory tax rate	$ 376	$ 361	$ 171
Change in valuation allowance	218	(18)	124
Equity income and dividends	(87)	(60)	(33)
(Income) expense not resulting in tax impact, net	(157)	(152)	(32)
US tax effect of foreign earnings and dividends	521	302	15
Foreign tax credits	(759)	(293)	(4)
Other foreign tax rate differentials	(38)	(48)	(47)
Legislative changes	116	4	9
State income taxes, net of federal benefit	12	8	6
Other, net	11	18	(8)
Income tax provision (benefit)	$ 213	$ 122	$ 201
Effective income tax rate	20.00%	12.00%	41.00%