Consolidated Statements of Capitalization - Capital Stock - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Beginning balance	$ 3,303	$ 2,978	$ 2,764
Net income	370	341	316
Other comprehensive income, after tax	0	1	1
Equity contributions from Parent	395	345	190
Dividends to Parent	(373)	(362)	(292)
Other			(1)
Ending balance	3,695	3,303	2,978
Common Stock [Member]
Beginning balance	$ 2,990	$ 2,645	$ 2,456
Beginning balance	10	10	10
Equity contributions from Parent	$ 395	$ 345	$ 190
Other			(1)
Ending balance	$ 3,385	$ 2,990	$ 2,645
Ending balance	10	10	10
Retained Earnings [Member]
Beginning balance	$ 314	$ 335	$ 311
Net income	370	341	316
Dividends to Parent	(373)	(362)	(292)
Ending balance	311	314	335
Accumulated Other Comprehensive Loss [Member]
Beginning balance	(1)	(2)	(3)
Other comprehensive income, after tax		1	1
Ending balance	$ (1)	$ (1)	$ (2)