Benefit Plans (Assumptions Used To Measure Benefit Plans) (Details)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	5.52%	5.65%	5.36%
Discount rate for net periodic cost	5.65%	5.36%	5.54%
Expected rate of return on plan assets	7.60%	7.73%	7.80%
Interest crediting rate for Alliant Energy Cash Balance Pension Plan	5.60%	6.24%	10.75%
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	5.56%	5.66%	5.35%
Discount rate for net periodic cost	5.66%	5.35%	5.55%
Expected rate of return on plan assets	7.60%	7.60%	7.80%
Rate of compensation increase	4.00%	3.75%	3.30%
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	5.56%	5.66%	5.35%
Discount rate for net periodic cost	5.66%	5.35%	5.54%
Expected rate of return on plan assets	7.60%	7.80%	7.80%
Rate of compensation increase	3.75%	3.50%	3.30%
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	5.40%	5.62%	5.40%
Discount rate for net periodic cost	5.62%	5.40%	5.53%
Expected rate of return on plan assets	6.37%	6.22%	6.50%
Other Postretirement Benefits Plans [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	5.38%	5.61%	5.40%
Discount rate for net periodic cost	5.61%	5.40%	5.53%
Expected rate of return on plan assets	6.70%	6.60%	6.90%
Other Postretirement Benefits Plans [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	5.38%	5.61%	5.40%
Discount rate for net periodic cost	5.61%	5.40%	5.53%
Expected rate of return on plan assets	5.75%	5.61%	5.65%
Minimum [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	3.75%	3.50%	3.30%
Maximum [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	4.50%	4.50%	4.50%