Benefit Plans (Fair Value Of Plan Assets By Asset Category And Fair Value Hierarchy Level) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 1,022.9	$ 965.6	$ 897.4
Total plan assets	1,022.9	965.6
Pension Plans, Defined Benefit [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	32.6	43.9
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	32.6	43.9
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	134.1	129.0
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	134.1	129.0
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	77.0	107.9
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	77.0	107.9
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	77.4	105.8
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	77.4	105.8
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	20.7	30.4
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	20.7	30.4
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	20.8	25.0
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	20.8	25.0
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	136.3	153.7
Pension Plans, Defined Benefit [Member] | International - Developed Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	68.0	80.3
Pension Plans, Defined Benefit [Member] | International - Developed Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	68.3	73.4
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	48.4	38.5
Pension Plans, Defined Benefit [Member] | International - Emerging Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48.4	38.5
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	99.1	94.5
Pension Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	56.7	56.3
Pension Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	42.4	38.2
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	96.1	0
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	96.1	0
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	29.2	30.7
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	29.2	30.7
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	49.1	49.2
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	49.1	49.2
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	202.2	162.6
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	202.0	162.4
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] | Securities Lending Invested Collateral [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	4.4
Pension Plans, Defined Benefit [Member] | Securities Lending Invested Collateral [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Securities Lending Invested Collateral [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	2.9
Pension Plans, Defined Benefit [Member] | Securities Lending Invested Collateral [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1.5
Pension Plans, Defined Benefit [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,023.0	975.6
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	328.2	329.3
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	694.8	644.8
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1.5
Pension Plans, Defined Benefit [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.7	0.6
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	485.9	458.8	426.1
Total plan assets	485.9	458.8
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.4	20.8
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	15.4	20.8
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	63.7	61.3
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	63.7	61.3
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
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	36.6	51.3
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	36.6	51.3
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	36.8	50.3
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	36.8	50.3
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	9.8	14.4
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	9.8	14.4
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	9.9	11.9
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	9.9	11.9
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	64.8	73.0
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	32.3	38.2
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	32.5	34.8
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	23.0	18.3
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	23.0	18.3
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	47.1	44.9
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	27.0	26.7
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	20.1	18.2
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	45.7	0
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	45.7	0
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	13.9	14.6
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	13.9	14.6
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	23.3	23.4
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	23.3	23.4
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	96.1	77.3
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	96.0	77.2
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] | Securities Lending Invested Collateral [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	2.1
Pension Plans, Defined Benefit [Member] | IPL [Member] | Securities Lending Invested Collateral [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Securities Lending Invested Collateral [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1.4
Pension Plans, Defined Benefit [Member] | IPL [Member] | Securities Lending Invested Collateral [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.7
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	486.1	463.6
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	156.0	156.5
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	330.1	306.4
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.7
Pension Plans, Defined Benefit [Member] | IPL [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	0.3
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	438.8	415.4	386.6
Total plan assets	438.8	415.4
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14.0	18.9
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	14.0	18.9
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	57.5	55.5
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	57.5	55.5
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	33.1	46.4
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	33.1	46.4
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	33.2	45.5
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	33.2	45.5
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	8.9	13.1
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	8.9	13.1
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	8.9	10.8
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	8.9	10.8
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	58.5	66.1
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	29.2	34.5
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	29.3	31.6
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	20.8	16.6
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	20.8	16.6
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	42.5	40.6
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	24.3	24.2
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	18.2	16.4
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
Pension Plans, Defined Benefit [Member] | WPL [Member] | Risk Parity Allocation Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	41.2	0
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	41.2	0
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	12.5	13.2
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	12.5	13.2
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	21.0	21.2
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	21.0	21.2
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	86.8	70.0
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	86.7	69.9
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] | Securities Lending Invested Collateral [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1.9
Pension Plans, Defined Benefit [Member] | WPL [Member] | Securities Lending Invested Collateral [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Securities Lending Invested Collateral [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1.2
Pension Plans, Defined Benefit [Member] | WPL [Member] | Securities Lending Invested Collateral [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.7
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	438.9	419.8
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	140.8	141.7
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	298.1	277.4
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.7
Pension Plans, Defined Benefit [Member] | WPL [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	0.2
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	124.9	123.1	120.4
Total plan assets	124.9	123.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.9	8.4
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	3.9	8.4
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	36.8	32.9
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	36.8	32.9
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	2.8
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	2.8
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	1.7	2.4
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	1.7	2.4
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	1.7	2.3
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	1.7	2.3
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	0.5	0.7
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	0.5	0.7
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	0.5	0.6
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	0.5	0.6
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	15.4	14.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Blend [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.4	14.3
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	3.0	3.4
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	1.5	1.8
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	1.5	1.6
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	1.1	0.8
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	1.1	0.8
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	30.4	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	29.5	29.6
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	0.8
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	2.1	0
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	2.1	0
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	0.6	0.7
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	0.6	0.7
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	1.1	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	1.1	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	23.2	22.4
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	18.8	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	4.4	3.6
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] | Securities Lending Invested Collateral [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | Securities Lending Invested Collateral [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Securities Lending Invested Collateral [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] | Securities Lending Invested Collateral [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	124.9	123.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	106.5	101.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18.4	21.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | Subtotal [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	81.2	78.8	74.7
Total plan assets	81.2	78.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.5	3.3
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	1.5	3.3
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	27.8	24.3
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	27.8	24.3
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	0.7	0.8
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	0.7	0.8
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	0.4	0.7
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	0.4	0.7
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	0.4	0.7
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	0.4	0.7
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	0.2
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	0.2
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	0.2
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	0.2
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	11.6	10.6
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	11.6	10.6
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	0.8	1.0
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	0.4	0.5
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	0.4	0.5
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	0.3	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	0.3	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
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	21.5
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	21.4	21.3
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	0.2	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	0.5	0
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	0.5	0
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	0.1	0.2
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	0.1	0.2
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	0.3	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	0.3	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	15.0	14.9
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	13.9	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	1.1	1.0
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] | IPL [Member] | Securities Lending Invested Collateral [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Securities Lending Invested Collateral [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] | Securities Lending Invested Collateral [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] | Securities Lending Invested Collateral [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] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	81.2	78.9
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	76.2	71.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.0	7.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [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	21.7	22.3	25.1
Total plan assets	21.7	22.3
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	3.9
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	3.9
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	3.1
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	3.1
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	1.5	1.3
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	1.5	1.3
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	1.2
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	1.2
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	1.1
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	1.1
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	0.3
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	0.3
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	0.3
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	0.3
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	1.5	1.3
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	1.5	1.3
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	1.5	1.6
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	0.7	0.8
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	0.8	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	0.4
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	0.4
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	3.6
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	3.2
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	0.4
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	0
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	0
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	0.3	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	0.3	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	0.5	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	0.5	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	4.0	3.5
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	2.2	1.7
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
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Securities Lending Invested Collateral [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Securities Lending Invested Collateral [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] | Securities Lending Invested Collateral [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] | Securities Lending Invested Collateral [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] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21.7	22.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13.1	12.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8.6	10.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Defined Benefit Plan Due To Borrowers For Securities Lending Program [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	(9.1)
Defined Benefit Plan Due To Borrowers For Securities Lending Program [Member] | Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	(4.3)
Defined Benefit Plan Due To Borrowers For Securities Lending Program [Member] | Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	(3.9)
Defined Benefit Plan Due To Borrowers For Securities Lending Program [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	(0.2)
Defined Benefit Plan Due To Borrowers For Securities Lending Program [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	(0.1)
Defined Benefit Plan Due To Borrowers For Securities Lending Program [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	(0.1)
Defined Benefit Plan Due To Brokers Net [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(0.8)	(1.5)
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	(0.4)	(0.8)
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	$ (0.3)	$ (0.7)