Exit Activities - Schedule of Retention Benefit Liability Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Restructuring Reserve [Roll Forward]
Other current liabilities	$ 162	$ 186
Retention Benefits | D.E. Karn Generating Complex
Restructuring Reserve [Roll Forward]
Retention benefit liability at beginning of period	4
Costs incurred and charged to expense	4
Retention benefit liability at the end of the period	8
Other current liabilities	$ 4