Variable Interest Entities - Net Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Noncontrolling interest	$ 218	$ 191
Great Valley Solar
Business Acquisition [Line Items]
Non-utility property, less accumulated depreciation	284	293
Other assets	39	40
Total assets	323	333
Other liabilities	13	17
Total liabilities	13	17
Accumulated depreciation	18	9
Copper Mountain Solar - Mesquite Solar
Business Acquisition [Line Items]
Non-utility property, less accumulated depreciation	446	461
Other assets	176	128
Total assets	622	589
Other liabilities	71	18
Total liabilities	71	18
Accumulated depreciation	30	15
Tax Equity Investors | Great Valley Solar
Business Acquisition [Line Items]
Noncontrolling interest	82	62
Tax Equity Investors | Copper Mountain Solar - Mesquite Solar
Business Acquisition [Line Items]
Noncontrolling interest	$ 134	$ 126