Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense (Benefit)						$ 347
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense (Benefit)						$ 1,100
Release of a valuation allowance on deferred tax assets, benefit				$ 28
One-time toll charge	$ 48			$ 48
Statutory U.S. income tax rate	21.00%		35.00%	21.00%	35.00%	35.00%
Foreign Earnings Repatriated				$ 2,200
Income Tax as result of agreement		$ 172		$ 172
Interest expense, net of tax benefit		$ 12
Maximum [Member]
Income tax examination period				2 years