Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income tax expense	$ 8	$ 31	$ 64	$ 76
Loss before income taxes	159	$ 784	1,640	$ 1,528
Tax Credit Carryforward, Valuation Allowance	11		11		$ 20
Unrecognized Tax Benefits	214		214
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 2		$ 2