Segment Information (Schedule of Other Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Segment Reporting Information [Line Items]
Cash and cash equivalents	$ 2	$ 13
Accounts receivable	408	368
Property, plant and equipment	4,446	4,111
Unamortized debt expense	18	20
Right-of-use lease assets	147	163
TOTAL ASSETS	5,394	$ 5,160	$ 4,555
Other
Segment Reporting Information [Line Items]
Cash and cash equivalents	2		10
Accounts receivable	3		0
Income taxes receivable	0		31
Prepayments	15		7
Property, plant and equipment	14		21
Unamortized debt expense	11		10
Right-of-use lease assets	67		77
Non-qualified retirement plan	4		5
Other	0		1
TOTAL ASSETS	$ 116		$ 162