Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements, Valuation Processes, Description	We estimate the fair value of our long-term, fixed rate debt using a Level 3 discounted cash flow analysis based on current borrowing rates for debt with similar maturities. We estimate the fair value of our long-term, variable rate debt using a Level 3 discounted cash flow analysis based on LIBOR rate forward curves.
Fair value of long-term debt, including current maturities	$ 1,590	$ 1,870
Unsecured Debt	$ 1,600	$ 1,830