CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDER'S EQUITY - USD ($) $ in Millions	Total	Common stock	Additional Paid In Capital	Retained Earnings
Balance (in shares) at Dec. 31, 2019		933,000
Beginning Balance at Dec. 31, 2019	$ 966	$ 93	$ 537	$ 336
Increase (Decrease) in Stockholder's Equity
Net income	85
Common dividends declared to parent	(55)			(55)
Contribution of capital by parent	41		41
Balance (in shares) at Sep. 30, 2020		933,000
Ending Balance at Sep. 30, 2020	1,037	$ 93	578	366
Balance (in shares) at Jun. 30, 2020		933,000
Beginning Balance at Jun. 30, 2020	1,015	$ 93	578	344
Increase (Decrease) in Stockholder's Equity
Net income	40			40
Common dividends declared to parent	(18)			(18)
Balance (in shares) at Sep. 30, 2020		933,000
Ending Balance at Sep. 30, 2020	$ 1,037	$ 93	578	366
Balance (in shares) at Dec. 31, 2020	933,000	933,000
Beginning Balance at Dec. 31, 2020	$ 1,068	$ 93	605	370
Increase (Decrease) in Stockholder's Equity
Net income	82
Common dividends declared to parent	(83)			(83)
Contribution of capital by parent	$ 36		36
Balance (in shares) at Sep. 30, 2021	933,000	933,000
Ending Balance at Sep. 30, 2021	$ 1,103	$ 93	641	369
Balance (in shares) at Jun. 30, 2021		933,000
Beginning Balance at Jun. 30, 2021	1,113	$ 93	638	382
Increase (Decrease) in Stockholder's Equity
Net income	36			36
Common dividends declared to parent	(49)			(49)
Contribution of capital by parent	$ 3		3
Balance (in shares) at Sep. 30, 2021	933,000	933,000
Ending Balance at Sep. 30, 2021	$ 1,103	$ 93	$ 641	$ 369