Fair Value Measurements - Additional Information (Details) - Clean Energy Businesses - Non-utility revenue - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gain (loss) on Level 3 energy derivative assets and liabilities	$ 2	$ (3)
Fair value, assets and liabilities measured on recurring basis, change in unrealized gain (loss)	$ 2	$ (3)