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
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$ 15	$ 14	$ 185
Unrecognized tax benefits, additions based on current period tax positions	0	0	0
Unrecognized tax benefits, additions for prior period tax positions	29	3	12
Unrecognized tax benefits, reductions for prior period tax positions	0	(1)	0
Unrecognized tax benefits, decrease resulting from settlements	0	0	(182)
Unrecognized tax benefits, reduction resulting from expiration of statue of limitations	0	(1)	(1)
Unrecognized tax benefits	$ 44	$ 15	$ 14