Income Taxes (Schedule of Unrecognized Tax Benefits Roll Forward) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	$ 1,736	$ 1,557	$ 1,617
Gross increases – tax positions in prior periods	87	3	17
Gross decreases – tax positions in prior periods	(410)	(44)	(348)
Gross increases – current-period tax positions	1,208	220	344
Settlements	(206)		(73)
Unrecognized tax benefits – December 31	2,412	$ 1,736	$ 1,557
Statute Lapse	$ (3)