Variable Interest Entities - Net Assets (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Noncontrolling interest	$ 206	$ 191
Great Valley Solar
Variable Interest Entity [Line Items]
Non-utility property, less accumulated depreciation	291	293
Other assets	41	40
Total assets	332	333
Other liabilities	16	17
Total liabilities	16	17
Accumulated depreciation	11	9
Great Valley Solar | Tax Equity Investors
Variable Interest Entity [Line Items]
Noncontrolling interest	66	62
Copper Mountain - Mesquite Solar
Variable Interest Entity [Line Items]
Non-utility property, less accumulated depreciation	456	461
Other assets	181	128
Total assets	637	589
Other liabilities	67	18
Total liabilities	67	18
Accumulated depreciation	19	15
Copper Mountain - Mesquite Solar | Tax Equity Investors
Variable Interest Entity [Line Items]
Noncontrolling interest	$ 137	$ 126