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	46
Common dividends declared to parent	(37)			(37)
Contribution of capital by parent	40		40
Balance (in shares) at Jun. 30, 2020		933,000
Ending Balance at Jun. 30, 2020	1,015	$ 93	577	345
Balance (in shares) at Mar. 31, 2020		933,000
Beginning Balance at Mar. 31, 2020	993	$ 93	547	353
Increase (Decrease) in Stockholder's Equity
Net income	12			12
Common dividends declared to parent	(20)			(20)
Contribution of capital by parent	30		30
Balance (in shares) at Jun. 30, 2020		933,000
Ending Balance at Jun. 30, 2020	$ 1,015	$ 93	577	345
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	46
Common dividends declared to parent	(34)			(34)
Contribution of capital by parent	$ 33		33
Balance (in shares) at Jun. 30, 2021	933,000	933,000
Ending Balance at Jun. 30, 2021	$ 1,113	$ 93	638	382
Balance (in shares) at Mar. 31, 2021		933,000
Beginning Balance at Mar. 31, 2021	1,110	$ 93	635	382
Increase (Decrease) in Stockholder's Equity
Net income	14			14
Common dividends declared to parent	(14)			(14)
Contribution of capital by parent	$ 3		3
Balance (in shares) at Jun. 30, 2021	933,000	933,000
Ending Balance at Jun. 30, 2021	$ 1,113	$ 93	$ 638	$ 382