Investment in Equity Method Affiliate - Schedule of Investments (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Equity Method Investment, Summarized Financial Information [Abstract]
Equity in earnings of equity method affiliate		$ 5	$ 4	$ 11	$ 7
Distributions from Equity Method Affiliates:
Return on investment in equity method affiliate				11	7
Return of investment in equity method affiliate				8	9
Operating income		80	167	226	332
Net income		44	124	149	247
SESH
Equity Method Investment, Summarized Financial Information [Abstract]
Equity in earnings of equity method affiliate		5	4	11	7
Distributions from Equity Method Affiliates:
Distributions from equity method affiliate	[1]	9	4	19	16
Return on investment in equity method affiliate		5	4	11	7
Return of investment in equity method affiliate		4	0	8	9
Revenues		28	27	55	54
Operating income		13	11	29	22
Net income		$ 10	$ 7	$ 21	$ 14

[1] Distributions from equity method affiliate includes a $5 million and $4 million return on investment and a $4 million and $0 return of investment for the three months ended June 30, 2020 and 2019, respectively. Distributions from equity method affiliate includes an $11 million and $7 million return on investment and an $8 million and $9 million return of investment for the six months ended June 30, 2020 and 2019, respectively.