Consolidated Statements of Changes in Common Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Retained Earnings	AOCI	Noncontrolling Interest
Beginning balance at Dec. 31, 2018	$ 4,315	$ 2,860	$ 1,279	$ (3)	$ 179
Beginning balance (in shares) at Dec. 31, 2018		40
Cumulative-effect of change in accounting principle	0		1	(1)
Total comprehensive income (loss) available (attributable) to common shareholder	(1,173)		(1,187)		14
Capital contribution from parent	775	$ 775
Capital contribution returned to parent	(20)				(20)
Dividend to parent	(20)		(20)
Other	(1)		(1)
Ending balance at Jun. 30, 2019	3,876	$ 3,635	72	(4)	173
Ending balance (in shares) at Jun. 30, 2019		40
Beginning balance at Mar. 31, 2019	3,867	$ 3,535	151	(4)	185
Beginning balance (in shares) at Mar. 31, 2019		40
Total comprehensive income (loss) available (attributable) to common shareholder	(70)		(78)		8
Capital contribution from parent	100	$ 100
Capital contribution returned to parent	(20)				(20)
Other	(1)		(1)
Ending balance at Jun. 30, 2019	3,876	$ 3,635	72	(4)	173
Ending balance (in shares) at Jun. 30, 2019		40
Beginning balance at Dec. 31, 2019	3,892	$ 3,695	20	(3)	180
Beginning balance (in shares) at Dec. 31, 2019		40
Total comprehensive income (loss) available (attributable) to common shareholder	160		157		3
Ending balance at Jun. 30, 2020	4,052	$ 3,695	177	(3)	183
Ending balance (in shares) at Jun. 30, 2020		40
Beginning balance at Mar. 31, 2020	3,985	$ 3,695	108	(3)	185
Beginning balance (in shares) at Mar. 31, 2020		40
Total comprehensive income (loss) available (attributable) to common shareholder	67		69		(2)
Ending balance at Jun. 30, 2020	$ 4,052	$ 3,695	$ 177	$ (3)	$ 183
Ending balance (in shares) at Jun. 30, 2020		40