Acquisitions, Discontinued Operations and Dispositions - Acquisitions (Details) $ in Millions	Aug. 01, 2019 USD ($) state customer	Jun. 01, 2018 USD ($) state customer
XOOM Energy, LLC
Business Acquisition [Line Items]
Increase in retail portfolio by RCE's acquired		395,000
Customers acquired		300,000
States in which entity operates | state		19
Purchase price | $		$ 213
Subsequent Event | Stream Energy Acquisition
Business Acquisition [Line Items]
Cash paid to acquire business | $	$ 300
Working capital adjustment | $	$ 25
Increase in retail portfolio by RCE's acquired	600,000
Customers acquired	450,000
States in which entity operates | state	9