Income Taxes - Interest Expense (Benefit), Net of Federal and State Income Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Interest Expense (Benefit) Net of Federal and State Income Tax Benefits
Recognized in income statements	$ 14	$ 56	$ 8
Accrued at end of period	$ 142	$ 134	$ 92