Summary of Significant Accounting Policies (Schedule of Cash Received and Allocated Losses from Subsidiaries, Noncontrolling Interest) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash received for the sale of noncontrolling interest to tax equity members	$ 426	$ 428
Cash received for the sale of noncontrolling interest to pro rata share members		415
Total Noncontrolling Interest Capital Contributions	426	843	$ 41
Allocated losses to noncontrolling tax equity members utilizing the HLBV method	271	165
Allocated losses to noncontrolling members based on pro rata shares of ownership	24	12
Total Noncontrolling Interest Allocated Losses	$ 295	$ 177