Income Taxes (Schedule of Unrecognized Tax Benefits and Liability for Contingent Income Taxes, Interest and Penalties) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$ 63	$ 56	$ 145	$ 79
Accrued interest and penalties	16	12	23
Tax credits and other indirect benefits	(12)	(14)	(35)
Liability for tax contingencies	$ 67	$ 54	$ 133