Fair Value Measurements, Including Derivatives (Schedule of Liabilities Measured at Fair Value on Recurring Basis) (Details) - Fair value, recurring - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Liabilities
Total liabilities	$ 18	$ 27
Interest Rate Contract [Member]
Liabilities
Total liabilities	18	27
Level 1
Liabilities
Total liabilities	0	0
Level 1 | Interest Rate Contract [Member]
Liabilities
Total liabilities	0	0
Level 2
Liabilities
Total liabilities	18	27
Level 2 | Interest Rate Contract [Member]
Liabilities
Total liabilities	18	27
Level 3
Liabilities
Total liabilities	0	0
Level 3 | Interest Rate Contract [Member]
Liabilities
Total liabilities	$ 0	$ 0