Stock-Based Compensation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock-based compensation
Pre-tax compensation expense	$ 9	$ 9	$ 51	$ 35
Long-term stock awards
Stock-based compensation
Pre-tax compensation expense	2	4	8	11
Stock options
Stock-based compensation
Pre-tax compensation expense	1	1	6	6
Restricted stock units
Stock-based compensation
Pre-tax compensation expense	3	1	26	12
Performance Restricted Stock Units
Stock-based compensation
Pre-tax compensation expense	2	2	8	3
Phantom stock awards
Stock-based compensation
Pre-tax compensation expense	$ 1	$ 1	$ 3	$ 3