Fair Value Measurements (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Assets:
Money market fund investments	$ 32	$ 44
Deferred proceeds	214	188
Liabilities and equity:
Long-term debt (including current maturities)	8,330	8,109
Commodity Contracts [Member]
Assets:
Derivatives	176	34
Liabilities and equity:
Derivatives	9	25
Level 1 [Member]
Assets:
Money market fund investments	32	44
Deferred proceeds	0	0
Liabilities and equity:
Long-term debt (including current maturities)	0	0
Level 1 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	0	0
Liabilities and equity:
Derivatives	0	0
Level 2 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities and equity:
Long-term debt (including current maturities)	8,329	8,107
Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	146	5
Liabilities and equity:
Derivatives	8	25
Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	214	188
Liabilities and equity:
Long-term debt (including current maturities)	1	2
Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	30	29
Liabilities and equity:
Derivatives	1	0
Carrying Amount [Member]
Assets:
Money market fund investments	32	44
Deferred proceeds	214	188
Liabilities and equity:
Long-term debt (including current maturities)	7,368	6,777
Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	176	34
Liabilities and equity:
Derivatives	9	25
IPL [Member]
Assets:
Money market fund investments	32	44
Deferred proceeds	214	188
Liabilities and equity:
Long-term debt (including current maturities)	4,124	4,021
IPL [Member] | Commodity Contracts [Member]
Assets:
Derivatives	84	29
Liabilities and equity:
Derivatives	4	12
IPL [Member] | Level 1 [Member]
Assets:
Money market fund investments	32	44
Deferred proceeds	0	0
Liabilities and equity:
Long-term debt (including current maturities)	0	0
IPL [Member] | Level 1 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	0	0
Liabilities and equity:
Derivatives	0	0
IPL [Member] | Level 2 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities and equity:
Long-term debt (including current maturities)	4,124	4,021
IPL [Member] | Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	65	3
Liabilities and equity:
Derivatives	3	12
IPL [Member] | Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	214	188
Liabilities and equity:
Long-term debt (including current maturities)	0	0
IPL [Member] | Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	19	26
Liabilities and equity:
Derivatives	1	0
IPL [Member] | Carrying Amount [Member]
Assets:
Money market fund investments	32	44
Deferred proceeds	214	188
Liabilities and equity:
Long-term debt (including current maturities)	3,643	3,345
IPL [Member] | Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	84	29
Liabilities and equity:
Derivatives	4	12
WPL [Member]
Liabilities and equity:
Long-term debt (including current maturities)	2,862	2,690
WPL [Member] | Commodity Contracts [Member]
Assets:
Derivatives	92	5
Liabilities and equity:
Derivatives	5	13
WPL [Member] | Level 1 [Member]
Liabilities and equity:
Long-term debt (including current maturities)	0	0
WPL [Member] | Level 1 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	0	0
Liabilities and equity:
Derivatives	0	0
WPL [Member] | Level 2 [Member]
Liabilities and equity:
Long-term debt (including current maturities)	2,862	2,690
WPL [Member] | Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	81	2
Liabilities and equity:
Derivatives	5	13
WPL [Member] | Level 3 [Member]
Liabilities and equity:
Long-term debt (including current maturities)	0	0
WPL [Member] | Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	11	3
Liabilities and equity:
Derivatives	0	0
WPL [Member] | Carrying Amount [Member]
Liabilities and equity:
Long-term debt (including current maturities)	2,429	2,130
WPL [Member] | Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	92	5
Liabilities and equity:
Derivatives	$ 5	$ 13