Benefit Plans (Assumptions Used To Measure Benefit Plans) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	4.47%	4.18%	4.97%
Discount rate for net periodic cost	4.18%	4.97%	4.11%
Expected rate of return on plan assets	7.60%	7.60%	7.60%
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	4.50%	4.20%	5.05%
Discount rate for net periodic cost	4.20%	5.05%	4.20%
Expected rate of return on plan assets	7.60%	7.60%	7.60%
Rate of compensation increase	3.65%	3.50%	3.50%
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	4.51%	4.20%	5.05%
Discount rate for net periodic cost	4.20%	5.05%	4.20%
Expected rate of return on plan assets	7.60%	7.60%	7.60%
Rate of compensation increase	3.65%	3.50%	3.50%
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	4.30%	3.97%	4.59%
Discount rate for net periodic cost	3.97%	4.59%	3.82%
Expected rate of return on plan assets	6.20%	7.40%	7.40%
Rate of compensation increase			3.50%
Medical cost trend on covered charges, initial trend rate (end of year)	7.25%	6.75%	7.00%
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	4.28%	3.94%	4.55%
Discount rate for net periodic cost	3.94%	4.55%	3.76%
Expected rate of return on plan assets	6.60%	7.60%	7.50%
Rate of compensation increase			3.50%
Medical cost trend on covered charges, initial trend rate (end of year)	7.25%	6.75%	7.00%
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	4.28%	3.96%	4.56%
Discount rate for net periodic cost	3.96%	4.56%	3.81%
Expected rate of return on plan assets	4.60%	7.30%	7.20%
Rate of compensation increase			3.50%
Medical cost trend on covered charges, initial trend rate (end of year)	7.25%	6.75%	7.00%
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	3.65%	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%