Equity (Compensation Expense Related to Stock-Based Compensation - Related to Phantom Stock-Based Awards) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	$ 127	$ 150	$ 86
Income tax benefit	27	32	18
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	6	7	6
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	63	89	23
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	$ 58	$ 54	$ 57