Income Taxes, Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Narrative
Income tax benefit resulting from effect of tax reform adjustments	$ 1,862
Income tax benefit from the remeasurement of U.S. deferred income tax assets and liabilities	2,643
Tax on the deemed repatriation of the accumulated earnings and profits of our international subsidiaries	734
Cumulative undistributed earnings and profits of international subsidiaries	4,700
Recognition of foreign withholding tax, net of U.S. federal tax benefit	47
Increase in valuation allowance	124
Cash and temporary cash investments	5,850	$ 4,816	$ 4,114	$ 3,689
Tax refund claim not presented in our balance sheets	274	433
Income tax benefits if recognized that would impact the effective tax rate	793	756
Interest expense and penalties accrued	77	$ 70
International subsidiaries [Member]
Income Tax Narrative
Cash and temporary cash investments	$ 3,200