Income Taxes (Details Textuals) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Taxes (Textuals)
Unrecognized tax benefits change as a result of potential resolutions of prior years' tax	$ 330			$ 330
Actual tax rates	21.90%		25.80%	21.90%	29.70%
Unrecognized tax benefits that, if recognized, could impact effective tax rate.	$ 294			$ 294
U.S. Tax Act Discrete Net Charge		$ 2,600
Internal Revenue Service (IRS) [Member] | Earliest Year [Member]
Income Tax Contingency [Line Items]
Open tax years by major tax jurisdiction	2008
Internal Revenue Service (IRS) [Member] | Latest Year [Member]
Income Tax Contingency [Line Items]
Open tax years by major tax jurisdiction	2014