Income Taxes (Net Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Components of Deferred Tax Assets and Liabilities [Abstract]
Deferred tax assets	$ 11,600	$ 10,722
Deferred tax liabilities	(9,430)	(10,334)
Valuation allowance	(3,094)	(118)
Deferred Tax Liabilities, Net	$ 924	$ 270