Benefit Plans (Fair Value Of Plan Assets By Asset Category And Fair Value Hierarchy Level) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 1,018.1	$ 1,022.9	$ 965.6
Total plan assets	1,018.1	1,022.9
Pension Plans, Defined Benefit [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	49.3	32.6
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
Pension Plans, Defined Benefit [Member] | Cash and Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	49.3	32.6
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
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	137.2	134.1
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	137.2	134.1
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
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
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	72.2	77.0
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
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	72.2	77.0
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
Pension Plans, Defined Benefit [Member] | U.S. Large Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	73.2	77.4
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
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	73.2	77.4
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
Pension Plans, Defined Benefit [Member] | U.S. Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.2	20.7
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
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	15.2	20.7
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
Pension Plans, Defined Benefit [Member] | U.S. Small Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.9	20.8
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	15.9	20.8
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
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
Pension Plans, Defined Benefit [Member] | International - Developed Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	102.9	136.3
Pension Plans, Defined Benefit [Member] | International - Developed Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52.1	68.0
Pension Plans, Defined Benefit [Member] | International - Developed Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50.8	68.3
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
Pension Plans, Defined Benefit [Member] | International - Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47.2	48.4
Pension Plans, Defined Benefit [Member] | International - Emerging Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47.2	48.4
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
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
Pension Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	99.9	99.1
Pension Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	57.2	56.7
Pension Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	42.7	42.4
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
Pension Plans, Defined Benefit [Member] | Risk Parity Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	102.5	96.1
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
Pension Plans, Defined Benefit [Member] | Risk Parity Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	102.5	96.1
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
Pension Plans, Defined Benefit [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	29.2
Pension Plans, Defined Benefit [Member] | Corporate Bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	29.2
Pension Plans, Defined Benefit [Member] | Corporate Bonds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Government and Agency Obligation [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	49.1
Pension Plans, Defined Benefit [Member] | Government and Agency Obligation [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Government and Agency Obligation [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	49.1
Pension Plans, Defined Benefit [Member] | Government and Agency Obligation [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	302.7	202.2
Pension Plans, Defined Benefit [Member] | Fixed Income Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	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	302.5	202.0
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
Pension Plans, Defined Benefit [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,018.3	1,023.0
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	309.8	328.2
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	708.5	694.8
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.7
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	484.7	485.9	458.8
Total plan assets	484.7	485.9
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	23.5	15.4
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
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	23.5	15.4
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
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	65.3	63.7
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	65.3	63.7
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
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
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	34.4	36.6
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
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	34.4	36.6
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
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Large Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	34.9	36.8
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
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	34.9	36.8
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
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7.2	9.8
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
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	7.2	9.8
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
Pension Plans, Defined Benefit [Member] | IPL [Member] | U.S. Small Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7.6	9.9
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	7.6	9.9
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
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
Pension Plans, Defined Benefit [Member] | IPL [Member] | International - Developed Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	49.0	64.8
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	24.8	32.3
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	24.2	32.5
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
Pension Plans, Defined Benefit [Member] | IPL [Member] | International - Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22.5	23.0
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	22.5	23.0
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
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
Pension Plans, Defined Benefit [Member] | IPL [Member] | Global Asset Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47.5	47.1
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	27.2	27.0
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	20.3	20.1
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
Pension Plans, Defined Benefit [Member] | IPL [Member] | Risk Parity Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48.8	45.7
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
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	48.8	45.7
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
Pension Plans, Defined Benefit [Member] | IPL [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	13.9
Pension Plans, Defined Benefit [Member] | IPL [Member] | Corporate Bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	13.9
Pension Plans, Defined Benefit [Member] | IPL [Member] | Corporate Bonds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Government and Agency Obligation [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	23.3
Pension Plans, Defined Benefit [Member] | IPL [Member] | Government and Agency Obligation [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Government and Agency Obligation [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	23.3
Pension Plans, Defined Benefit [Member] | IPL [Member] | Government and Agency Obligation [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	144.1	96.1
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	0.1	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	144.0	96.0
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
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	484.8	486.1
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	147.5	156.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	337.3	330.1
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
Pension Plans, Defined Benefit [Member] | IPL [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.2
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	440.3	438.8	415.4
Total plan assets	440.3	438.8
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21.3	14.0
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
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	21.3	14.0
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
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	59.3	57.5
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	59.3	57.5
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
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
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	31.3	33.1
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
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	31.3	33.1
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
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Large Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	31.7	33.2
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
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	31.7	33.2
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
Pension Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.6	8.9
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
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	6.6	8.9
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
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	8.9
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	8.9
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
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
Pension Plans, Defined Benefit [Member] | WPL [Member] | International - Developed Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44.5	58.5
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	22.5	29.2
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	22.0	29.3
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
Pension Plans, Defined Benefit [Member] | WPL [Member] | International - Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	20.4	20.8
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	20.4	20.8
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
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
Pension Plans, Defined Benefit [Member] | WPL [Member] | Global Asset Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	43.2	42.5
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	24.8	24.3
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	18.4	18.2
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
Pension Plans, Defined Benefit [Member] | WPL [Member] | Risk Parity Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44.3	41.2
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
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	44.3	41.2
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
Pension Plans, Defined Benefit [Member] | WPL [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	12.5
Pension Plans, Defined Benefit [Member] | WPL [Member] | Corporate Bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	12.5
Pension Plans, Defined Benefit [Member] | WPL [Member] | Corporate Bonds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Government and Agency Obligation [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	21.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Government and Agency Obligation [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Government and Agency Obligation [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	21.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Government and Agency Obligation [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	130.9	86.8
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	0.1	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	130.8	86.7
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
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	440.4	438.9
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	134.0	140.8
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	306.4	298.1
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
Pension Plans, Defined Benefit [Member] | WPL [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.2
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	121.6	124.9	123.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	103.8	106.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17.8	18.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.7	3.9
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
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	3.7	3.9
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35.8	36.8
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	35.8	36.8
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
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.9	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	2.9	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
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.5	1.7
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
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	1.5	1.7
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Large Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.6	1.7
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
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	1.6	1.7
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.3	0.5
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
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	0.3	0.5
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Small Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.4	0.5
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	0.4	0.5
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
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14.2	15.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Blend [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14.2	15.4
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
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Developed Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.2	3.0
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	1.1	1.5
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	1.1	1.5
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.0	1.1
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	1.0	1.1
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
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	30.3	30.4
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	29.4	29.5
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	0.9	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
Other Postretirement Benefit Plans, Defined Benefit [Member] | Risk Parity Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.2	2.1
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
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	2.2	2.1
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | Corporate Bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | Corporate Bonds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Government and Agency Obligation [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | Government and Agency Obligation [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Government and Agency Obligation [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | Government and Agency Obligation [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25.5	23.2
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	19.0	18.8
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	6.5	4.4
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	78.7	81.2	78.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	74.7	76.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4.0	5.0
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.4	1.5
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
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	1.4	1.5
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27.2	27.8
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	27.2	27.8
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
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
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	0.5	0.7
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	0.5	0.7
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
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
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	0.3	0.4
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
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	0.3	0.4
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
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	0.3	0.4
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
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	0.3	0.4
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
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	0.1	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
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	0.1	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
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	0.1	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	0.1	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
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
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	11.6
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	11.6
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
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Developed Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.4	0.8
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	0.2	0.4
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	0.2	0.4
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | International - Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	0.3
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	0.2	0.3
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
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
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	21.6	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	21.5	21.4
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	0.1	0.2
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
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	0.4	0.5
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
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	0.4	0.5
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Corporate Bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Corporate Bonds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Government and Agency Obligation [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Government and Agency Obligation [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Government and Agency Obligation [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Government and Agency Obligation [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	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	15.5	15.0
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	14.3	13.9
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	1.2	1.1
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21.8	21.7	22.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13.0	13.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8.8	8.6
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.4	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
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	1.4	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
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.6	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	3.6	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
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
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	1.6	1.5
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	1.6	1.5
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
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
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	0.8	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
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	0.8	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
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	0.8	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
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	0.8	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
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	0.2	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
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	0.2	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
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	0.2	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	0.2	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
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.4	1.5
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	1.4	1.5
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
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Developed Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.2	1.5
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	0.6	0.7
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	0.6	0.8
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.5	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	0.5	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
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
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	3.8	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	3.3	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	0.5	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
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	1.1	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
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	1.1	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
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Corporate Bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Corporate Bonds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Government and Agency Obligation [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Government and Agency Obligation [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Government and Agency Obligation [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Government and Agency Obligation [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	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	5.2	4.0
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	1.8	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	3.4	2.2
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
Defined Benefit Plan Due To Brokers Net [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(0.3)	(0.8)
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	(0.2)	(0.4)
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	$ (0.1)	$ (0.3)