CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDER'S EQUITY - USD ($) $ in Millions	Total	Common stock	Additional Paid In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance (in shares) at Dec. 31, 2019		100
Beginning Balance at Dec. 31, 2019	$ 6,996	$ 0	$ 4,940	$ 2,083	$ (27)
Increase (Decrease) in Stockholder's Equity
Net income	455			455
Total other comprehensive income	1				1
Dividends declared to parent	(694)			(694)
Contribution of capital by parent	754		754
Adoption of ASC Topic 326	(1)			(1)
Balance (in shares) at Sep. 30, 2020		100
Ending Balance at Sep. 30, 2020	7,511	$ 0	5,694	1,843	(26)
Balance (in shares) at Jun. 30, 2020		100
Beginning Balance at Jun. 30, 2020	7,420	$ 0	5,694	1,752	(26)
Increase (Decrease) in Stockholder's Equity
Net income	218			218
Total other comprehensive income	0
Dividends declared to parent	(127)			(127)
Balance (in shares) at Sep. 30, 2020		100
Ending Balance at Sep. 30, 2020	$ 7,511	$ 0	5,694	1,843	(26)
Balance (in shares) at Dec. 31, 2020	100	100
Beginning Balance at Dec. 31, 2020	$ 7,592	$ 0	5,770	1,846	(24)
Increase (Decrease) in Stockholder's Equity
Net income	516			516
Total other comprehensive income	1				1
Dividends declared to parent	(362)			(362)
Contribution of capital by parent	$ 563		563
Balance (in shares) at Sep. 30, 2021	100	100
Ending Balance at Sep. 30, 2021	$ 8,310	$ 0	6,333	2,000	(23)
Balance (in shares) at Jun. 30, 2021		100
Beginning Balance at Jun. 30, 2021	8,099	$ 0	6,210	1,912	(23)
Increase (Decrease) in Stockholder's Equity
Net income	215			215
Total other comprehensive income	0
Dividends declared to parent	(127)			(127)
Contribution of capital by parent	$ 123		123
Balance (in shares) at Sep. 30, 2021	100	100
Ending Balance at Sep. 30, 2021	$ 8,310	$ 0	$ 6,333	$ 2,000	$ (23)