Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Payments for income taxes, net of tax refunds received	$ (13)	$ (5)	$ 0
Unrecognized tax benefits	$ 0	$ 39	$ 141	$ 124