Income Taxes (Details Textuals) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Taxes (Textuals)
Unrecognized tax benefits as a result of potential resolutions of prior years' tax	$ 104
Decrease in Unrecognized tax benefits, amounts recorded to equity	$ 331
Actual tax rates	31.90%	34.70%
Tax Benefit Recognized in the period	$ 289
Unrecognized tax benefits that, if recognized, could impact effective tax rate.	$ 71
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