Income Taxes (Summary of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits — January 1	$ 136	$ 130	$ 67
Current year tax positions	3	0	56
Prior year tax positions		7	7
Prior year tax positions	(5)
Acquisitions	0	0	0
Settlements	(5)	(1)	0
Unrecognized tax benefits — December 31	$ 129	$ 136	$ 130