Investment in Equity Method Affiliate - Schedule of Investments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Equity in Earnings of Equity Method Affiliates:
Equity in earnings of equity method affiliate	$ 6	$ 3
Distributions from Equity Method Affiliates:
Return on investment in equity method affiliate	6	3
Return of investment in equity method affiliate	4	9
Operating income	146	165
Net income	105	123
SESH
Equity in Earnings of Equity Method Affiliates:
Equity in earnings of equity method affiliate	6	3
Distributions from Equity Method Affiliates:
Distributions from equity method affiliate	10	12
Return on investment in equity method affiliate	6	3
Return of investment in equity method affiliate	4	9
Revenues	27	27
Operating income	16	11
Net income	$ 11	$ 7