New Accounting Standards New Accounting Standards (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (20,861)	$ (20,022)	$ (18,976)	$ (19,225)
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (20,261)	$ (19,780)	$ (19,026)	(18,958)
Retained Earnings [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest				$ 8