Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Significant Accounting Policies [Line Items]
LIFO Inventory Amount	$ 101	$ 92
Cost of replacing inventories carried at LIFO cost less than carrying value	48
Interest Expense
Significant Accounting Policies [Line Items]
Interest and AFUDC debt	34	27	$ 36
Interest Expense | Indiana
Significant Accounting Policies [Line Items]
Interest and AFUDC debt	16	13	21
Other Income (Expense)
Significant Accounting Policies [Line Items]
AFUDC equity	28	25	22
Houston Electric | Interest Expense
Significant Accounting Policies [Line Items]
Interest and AFUDC debt	13	8	8
Houston Electric | Other Income (Expense)
Significant Accounting Policies [Line Items]
AFUDC equity	20	14	15
CERC Corp
Significant Accounting Policies [Line Items]
LIFO Inventory Amount	56	55
Cost of replacing inventories carried at LIFO cost less than carrying value	0
CERC Corp | Interest Expense
Significant Accounting Policies [Line Items]
Interest and AFUDC debt	2	3	3
CERC Corp | Other Income (Expense)
Significant Accounting Policies [Line Items]
AFUDC equity	$ 3	$ 3	$ 3