Segment Information (Schedule of Other Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Cash and cash equivalents	$ 13	$ 5
Current hedging asset	241	278
Property plant and equipment	4,111	5,267
Unamortized debt expense	20	19
Operating lease assets	163	159
TOTAL ASSETS	5,160	6,717	$ 5,797
Other
Segment Reporting Information [Line Items]
Cash and cash equivalents	13	5	205
Accounts receivable	1	0	4
Income taxes receivable	0	30	89
Current hedging asset	0	0	1
Prepayments	6	8	8
Property plant and equipment	16	27	60
Unamortized debt expense	11	11	11
Operating lease assets	72	80
Non-qualified retirement plan	6	7	8
TOTAL ASSETS	$ 125	$ 168	$ 386