Variable Interest Entities - Net Assets (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Noncontrolling interest	$ 217	$ 191
Great Valley Solar
Variable Interest Entity [Line Items]
Non-utility property, less accumulated depreciation	286	293
Other assets	41	40
Total assets	327	333
Other liabilities	15	17
Total liabilities	15	17
Accumulated depreciation	16	9
Great Valley Solar | Tax Equity Investors
Variable Interest Entity [Line Items]
Noncontrolling interest	78	62
Copper Mountain - Mesquite Solar
Variable Interest Entity [Line Items]
Non-utility property, less accumulated depreciation	449	461
Other assets	181	128
Total assets	630	589
Other liabilities	72	18
Total liabilities	72	18
Accumulated depreciation	26	15
Copper Mountain - Mesquite Solar | Tax Equity Investors
Variable Interest Entity [Line Items]
Noncontrolling interest	$ 137	$ 126