Benefit Plans (Assumptions Used To Measure Benefit Plans) (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	4.18%	4.97%	4.11%
Discount rate for net periodic cost	4.97%	4.11%	4.86%
Expected rate of return on plan assets	7.60%	7.60%	7.90%
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	4.20%	5.05%	4.20%
Discount rate for net periodic cost	5.05%	4.20%	4.95%
Expected rate of return on plan assets	7.60%	7.60%	7.90%
Rate of compensation increase	3.50%	3.50%	3.50%
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	4.20%	5.05%	4.20%
Discount rate for net periodic cost	5.05%	4.20%	4.95%
Expected rate of return on plan assets	7.60%	7.60%	7.90%
Rate of compensation increase	3.50%	3.50%	3.50%
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	3.97%	4.59%	3.82%
Discount rate for net periodic cost	4.59%	3.82%	4.60%
Expected rate of return on plan assets	7.40%	7.40%	7.50%
Rate of compensation increase		3.50%	3.50%
Medical cost trend on covered charges, initial trend rate (end of year)	6.75%	7.00%	7.50%
Medical cost trend on covered charges, ultimate trend rate	5.00%	5.00%	5.00%
Other Postretirement Benefits Plans [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	3.94%	4.55%	3.76%
Discount rate for net periodic cost	4.55%	3.76%	4.60%
Expected rate of return on plan assets	7.60%	7.50%	7.40%
Rate of compensation increase		3.50%	3.50%
Medical cost trend on covered charges, initial trend rate (end of year)	6.75%	7.00%	7.50%
Medical cost trend on covered charges, ultimate trend rate	5.00%	5.00%	5.00%
Other Postretirement Benefits Plans [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	3.96%	4.56%	3.81%
Discount rate for net periodic cost	4.56%	3.81%	4.60%
Expected rate of return on plan assets	7.30%	7.20%	7.00%
Rate of compensation increase		3.50%	3.50%
Medical cost trend on covered charges, initial trend rate (end of year)	6.75%	7.00%	7.50%
Medical cost trend on covered charges, ultimate trend rate	5.00%	5.00%	5.00%
Minimum [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	3.50%	3.50%	3.50%
Maximum [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	4.50%	4.50%	4.50%