Income Taxes (Schedule of Unrecognized Tax Benefits Roll Forward) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	$ 1,617	$ 1,312	$ 1,141
Gross increases – tax positions in prior periods	17	38	403
Gross decreases – tax positions in prior periods	(348)	(25)	(251)
Gross increases – current-period tax positions	344	292	217
Settlements	(73)		(197)
Lapse of statute of limitations			(1)
Unrecognized tax benefits – December 31	$ 1,557	$ 1,617	$ 1,312