Benefit Plans (Fair Value Of Plan Assets By Asset Category And Fair Value Hierarchy Level) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 895.0	$ 1,018.1	$ 1,022.9
Total plan assets	895.0	1,018.1
Pension Plans, Defined Benefit [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	23.1	49.3
Pension Plans, Defined Benefit [Member] | Cash and Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | Cash and Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	23.1	49.3
Pension Plans, Defined Benefit [Member] | Cash and Equivalents [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	100.4	137.2
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Core [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	100.4	137.2
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Core [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Core [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	59.9	72.2
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Value [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Value [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	59.9	72.2
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Value [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	60.5	73.2
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Growth [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Growth [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	60.5	73.2
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Growth [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | U.S. Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14.2	15.2
Pension Plans, Defined Benefit [Member] | U.S. Small Cap Value [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | U.S. Small Cap Value [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14.2	15.2
Pension Plans, Defined Benefit [Member] | U.S. Small Cap Value [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | U.S. Small Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16.0	15.9
Pension Plans, Defined Benefit [Member] | U.S. Small Cap Growth [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16.0	15.9
Pension Plans, Defined Benefit [Member] | U.S. Small Cap Growth [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | U.S. Small Cap Growth [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | International - Developed Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	104.4	102.9
Pension Plans, Defined Benefit [Member] | International - Developed Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52.7	52.1
Pension Plans, Defined Benefit [Member] | International - Developed Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51.7	50.8
Pension Plans, Defined Benefit [Member] | International - Developed Markets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | International - Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	41.2	47.2
Pension Plans, Defined Benefit [Member] | International - Emerging Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	41.2	47.2
Pension Plans, Defined Benefit [Member] | International - Emerging Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | International - Emerging Markets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	96.3	99.9
Pension Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52.9	57.2
Pension Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	43.4	42.7
Pension Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | Risk Parity Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	94.0	102.5
Pension Plans, Defined Benefit [Member] | Risk Parity Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | Risk Parity Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	94.0	102.5
Pension Plans, Defined Benefit [Member] | Risk Parity Allocation Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.1
Pension Plans, Defined Benefit [Member] | Corporate Bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.1
Pension Plans, Defined Benefit [Member] | Corporate Bonds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	284.8	302.7
Pension Plans, Defined Benefit [Member] | Fixed Income Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.2
Pension Plans, Defined Benefit [Member] | Fixed Income Funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	284.8	302.5
Pension Plans, Defined Benefit [Member] | Fixed Income Funds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	894.8	1,018.3
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	263.2	309.8
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	631.6	708.5
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	0.1
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	422.7	484.7	485.9
Total plan assets	422.7	484.7
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.9	23.5
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.9	23.5
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47.4	65.3
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Core [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47.4	65.3
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Core [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Core [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28.3	34.4
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Value [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Value [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28.3	34.4
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Value [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28.6	34.9
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Growth [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Growth [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28.6	34.9
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Growth [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.7	7.2
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Value [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Value [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.7	7.2
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Value [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7.5	7.6
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Growth [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7.5	7.6
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Growth [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Growth [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | International - Developed Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	49.3	49.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | International - Developed Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24.9	24.8
Pension Plans, Defined Benefit [Member] | IPL [Member] | International - Developed Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24.4	24.2
Pension Plans, Defined Benefit [Member] | IPL [Member] | International - Developed Markets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | International - Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19.5	22.5
Pension Plans, Defined Benefit [Member] | IPL [Member] | International - Emerging Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19.5	22.5
Pension Plans, Defined Benefit [Member] | IPL [Member] | International - Emerging Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | International - Emerging Markets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Global Asset Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	45.5	47.5
Pension Plans, Defined Benefit [Member] | IPL [Member] | Global Asset Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25.0	27.2
Pension Plans, Defined Benefit [Member] | IPL [Member] | Global Asset Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	20.5	20.3
Pension Plans, Defined Benefit [Member] | IPL [Member] | Global Asset Allocation Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Risk Parity Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44.4	48.8
Pension Plans, Defined Benefit [Member] | IPL [Member] | Risk Parity Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Risk Parity Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44.4	48.8
Pension Plans, Defined Benefit [Member] | IPL [Member] | Risk Parity Allocation Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	134.5	144.1
Pension Plans, Defined Benefit [Member] | IPL [Member] | Fixed Income Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.1
Pension Plans, Defined Benefit [Member] | IPL [Member] | Fixed Income Funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	134.5	144.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Fixed Income Funds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	422.6	484.8
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	124.3	147.5
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	298.3	337.3
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.1
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	386.8	440.3	438.8
Total plan assets	386.8	440.3
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.0	21.3
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.0	21.3
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and Equivalents [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	43.4	59.3
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Core [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	43.4	59.3
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Core [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Core [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25.9	31.3
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Value [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Value [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25.9	31.3
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Value [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26.2	31.7
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Growth [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Growth [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26.2	31.7
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Growth [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.1	6.6
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Value [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Value [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.1	6.6
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Value [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.9	6.9
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Growth [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.9	6.9
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Growth [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Growth [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | International - Developed Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	45.1	44.5
Pension Plans, Defined Benefit [Member] | WPL [Member] | International - Developed Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22.8	22.5
Pension Plans, Defined Benefit [Member] | WPL [Member] | International - Developed Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22.3	22.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | International - Developed Markets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | International - Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17.8	20.4
Pension Plans, Defined Benefit [Member] | WPL [Member] | International - Emerging Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17.8	20.4
Pension Plans, Defined Benefit [Member] | WPL [Member] | International - Emerging Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | International - Emerging Markets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Global Asset Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	41.6	43.2
Pension Plans, Defined Benefit [Member] | WPL [Member] | Global Asset Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22.8	24.8
Pension Plans, Defined Benefit [Member] | WPL [Member] | Global Asset Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18.8	18.4
Pension Plans, Defined Benefit [Member] | WPL [Member] | Global Asset Allocation Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Risk Parity Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40.6	44.3
Pension Plans, Defined Benefit [Member] | WPL [Member] | Risk Parity Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Risk Parity Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40.6	44.3
Pension Plans, Defined Benefit [Member] | WPL [Member] | Risk Parity Allocation Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	123.1	130.9
Pension Plans, Defined Benefit [Member] | WPL [Member] | Fixed Income Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.1
Pension Plans, Defined Benefit [Member] | WPL [Member] | Fixed Income Funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	123.1	130.8
Pension Plans, Defined Benefit [Member] | WPL [Member] | Fixed Income Funds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	386.7	440.4
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	113.7	134.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	273.0	306.4
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	106.9	121.6	124.9
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	97.8	103.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9.1	17.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.6	3.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.6	3.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and Equivalents [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21.1	35.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Blend [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21.1	35.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Blend [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Blend [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.9	2.9
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Core [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.9	2.9
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Core [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Core [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.5	1.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Value [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Value [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.5	1.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Value [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.5	1.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Growth [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Growth [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.5	1.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Growth [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Small Cap Value [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Small Cap Value [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Small Cap Value [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Small Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Small Cap Growth [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Small Cap Growth [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Small Cap Growth [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12.5	14.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Blend [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12.5	14.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Blend [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Blend [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Developed Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.0	2.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Developed Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.5	1.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Developed Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.5	1.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Developed Markets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.4	1.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Emerging Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.4	1.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Emerging Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Emerging Markets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16.4	30.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16.0	29.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.4	0.9
Other Postretirement Benefit Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Risk Parity Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.9	2.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | Risk Parity Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Risk Parity Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.9	2.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | Risk Parity Allocation Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48.9	25.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fixed Income Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	46.3	19.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fixed Income Funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.6	6.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fixed Income Funds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	69.2	78.7	81.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	67.7	74.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.5	4.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.9	1.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.9	1.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16.6	27.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Blend [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16.6	27.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Blend [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Blend [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Core [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Core [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Core [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Value [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Value [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Value [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Growth [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Growth [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Growth [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Value [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Value [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Value [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Growth [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Growth [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Growth [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.7	10.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Blend [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.7	10.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Blend [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Blend [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Developed Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Developed Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Developed Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Developed Markets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Emerging Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Emerging Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Emerging Markets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Global Asset Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.9	21.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Global Asset Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.9	21.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Global Asset Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Global Asset Allocation Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Risk Parity Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Risk Parity Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Risk Parity Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Risk Parity Allocation Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	33.6	15.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Fixed Income Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	33.3	14.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Fixed Income Funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.3	1.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Fixed Income Funds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18.7	21.8	$ 21.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16.4	13.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.3	8.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.3	1.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.3	1.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and Equivalents [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	3.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Blend [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	3.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Blend [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Blend [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	1.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Core [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	1.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Core [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Core [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Value [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Value [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Value [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Growth [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Growth [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Growth [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Value [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Value [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Value [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Growth [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Growth [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Growth [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	1.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Blend [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	1.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Blend [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Blend [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Developed Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	1.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Developed Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Developed Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Developed Markets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Emerging Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Emerging Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Emerging Markets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Global Asset Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.4	3.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Global Asset Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.4	3.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Global Asset Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Global Asset Allocation Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Risk Parity Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	1.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Risk Parity Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Risk Parity Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	1.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Risk Parity Allocation Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.0	5.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Fixed Income Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.0	1.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Fixed Income Funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	3.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Fixed Income Funds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Defined Benefit Plan Due To Brokers Net [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	(0.3)
Defined Benefit Plan Due To Brokers Net [Member] | Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	(0.2)
Defined Benefit Plan Due To Brokers Net [Member] | Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0.0	$ (0.1)