Notes Receivable - Schedule of Allowance For Loan Losses (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2020	Jan. 01, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201613Member
EnerBank
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 104	$ 33
Effects of new accounting standard	116	116	$ 116
Provisions for loan losses	19	45
Charge-offs	(9)	(29)
Recoveries	2	5
Balance at end of period	116	116
EnerBank | Cumulative effect of change in accounting principle
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	0	62
Effects of new accounting standard	$ 0	$ 62
Unfunded Loan Commitment | EnerBank
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit loss on off balance sheet commitments			$ 9
Unfunded Loan Commitment | EnerBank | Cumulative effect of change in accounting principle
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for expected credit loss on off balance sheet commitments				$ 3