Income Taxes (Schedule of Unrecognized Tax Benefits) (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]
Balance, January 1	$ 219	$ 102	$ 143
Additions for tax positions of the current year	21	25	14
Additions for tax positions of prior years	60	110	1
Reductions for tax positions of prior years	(5)	(1)	(33)
Settlements during the period	(8)	(10)	(20)
Lapses of applicable statute of limitation	(9)	(7)	(3)
Balance, December 31	$ 278	$ 219	$ 102