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, 2017		100
Beginning Balance at Dec. 31, 2017	$ 5,828	$ 0	$ 4,033	$ 1,822	$ (27)
Increase (Decrease) in Stockholder's Equity
Net income	552			552
Total other comprehensive income (loss)	1				1
Common dividends declared to parent	(391)			(391)
Contribution of capital by parent	308		308
Balance (in shares) at Dec. 31, 2018		100
Ending Balance at Dec. 31, 2018	6,298	$ 0	4,341	1,983	(26)
Increase (Decrease) in Stockholder's Equity
Net income	578			578
Total other comprehensive income (loss)	(1)				(1)
Common dividends declared to parent	(478)			(478)
Contribution of capital by parent	$ 599		599
Balance (in shares) at Dec. 31, 2019	100	100
Ending Balance at Dec. 31, 2019	$ 6,996	$ 0	4,940	2,083	(27)
Increase (Decrease) in Stockholder's Equity
Net income	588			588
Total other comprehensive income (loss)	3				3
Common dividends declared to parent	(824)			(824)
Contribution of capital by parent	830		830
Adoption of ASC Topic 326	$ (1)			(1)
Balance (in shares) at Dec. 31, 2020	100	100
Ending Balance at Dec. 31, 2020	$ 7,592	$ 0	$ 5,770	$ 1,846	$ (24)