Notes Receivable - Schedule of Allowance For Loan Losses (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Jun. 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	$ 99	$ 33
Effects of new accounting standard	104	104	$ 104
Provisions for loan losses	13	26
Charge-offs	(9)	(20)
Recoveries	1	3
Balance at end of period	104	104
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