Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income tax expense	$ 23	$ 44
Loss before income taxes	87	914
Tax Credit Carryforward, Valuation Allowance		$ 20
Unrecognized Tax Benefits	233
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 3