Basis of Presentation and Accounting Policies (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
New Accounting Pronouncements
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Shareholders' equity	$ (27,849)			$ (25,943)	$ (25,607)
Retained earnings [Member]
New Accounting Pronouncements
Shareholders' equity	$ (37,679)	$ (37,069)		(36,977)	$ (36,317)	$ (36,135)	$ (35,204)
Cumulative Effect, Period of Adoption, Adjustment [Member] | Retained earnings [Member]
New Accounting Pronouncements
Shareholders' equity			$ 43	$ 43