v2.4.0.6

Benefit Plans (Fair Value Of Plan Assets By Asset Category And Fair Value Hierarchy Level) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 965.6	$ 897.4	$ 823.0
Total plan assets	965.6	897.4
Pension Plans, Defined Benefit [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	43.9	117.5
Pension Plans, Defined Benefit [Member] | Cash and Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	117.5
Pension Plans, Defined Benefit [Member] | Cash and Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	43.9	0
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	129.0	110.7
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	129.0	110.7
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	107.9	91.6
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	107.9	91.6
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	105.8	91.5
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	105.8	91.5
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	30.4	25.7
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	30.4	25.7
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	25.0	21.7
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	25.0	21.7
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	153.7	126.4
Pension Plans, Defined Benefit [Member] | International - Developed Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	80.3	65.4
Pension Plans, Defined Benefit [Member] | International - Developed Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	73.4	61.0
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	38.5	30.4
Pension Plans, Defined Benefit [Member] | International - Emerging Markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38.5	30.4
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	94.5	0
Pension Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	56.3	0
Pension Plans, Defined Benefit [Member] | Global Asset Allocation Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38.2	0
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] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	30.7	57.1
Pension Plans, Defined Benefit [Member] | Corporate Bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	30.7	57.1
Pension Plans, Defined Benefit [Member] | Corporate Bonds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Government and Agency Obligation [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	49.2	87.8
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	49.2	87.8
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	162.6	146.7
Pension Plans, Defined Benefit [Member] | Fixed Income Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	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	162.4	146.5
Pension Plans, Defined Benefit [Member] | Fixed Income Funds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Securities Lending Invested Collateral [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4.4	9.3
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	4.7
Pension Plans, Defined Benefit [Member] | Securities Lending Invested Collateral [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.9	2.8
Pension Plans, Defined Benefit [Member] | Securities Lending Invested Collateral [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.5	1.8
Pension Plans, Defined Benefit [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	975.6	916.4
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	329.3	350.6
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	644.8	564.0
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.5	1.8
Pension Plans, Defined Benefit [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.6	1.0
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	322.3	298.7	256.9
Total plan assets	322.3	298.7
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14.6	39.1
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	39.1
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	14.6	0
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	43.1	36.8
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	43.1	36.8
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	36.0	30.5
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	36.0	30.5
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	35.3	30.5
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	35.3	30.5
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	10.2	8.6
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	10.2	8.6
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	8.3	7.2
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	8.3	7.2
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	51.3	42.1
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	26.8	21.8
Pension Plans, Defined Benefit [Member] | IPL [Member] | International - Developed Markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24.5	20.3
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	12.9	10.1
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	12.9	10.1
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	31.5	0
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	18.8	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	12.7	0
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] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.2	19.0
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	10.2	19.0
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	16.4	29.2
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	16.4	29.2
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	54.3	48.8
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	54.2	48.7
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	1.5	3.1
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	1.6
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	1.0	0.9
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	0.5	0.6
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	325.6	305.0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	110.0	116.7
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	215.1	187.7
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.5	0.6
Pension Plans, Defined Benefit [Member] | IPL [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	0.4
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	313.2	289.6	255.2
Total plan assets	313.2	289.6
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14.2	37.9
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	37.9
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	14.2	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	41.8	35.7
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	41.8	35.7
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	35.0	29.6
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	35.0	29.6
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	34.3	29.5
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	34.3	29.5
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	9.9	8.3
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	9.9	8.3
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	8.1	7.0
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	8.1	7.0
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	49.9	40.8
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	26.1	21.1
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	23.8	19.7
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	12.5	9.8
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	12.5	9.8
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	30.7	0
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	18.3	0
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	12.4	0
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] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9.9	18.4
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	9.9	18.4
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	16.0	28.3
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	16.0	28.3
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	52.8	47.4
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	52.7	47.3
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	1.4	3.0
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	1.5
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	0.9	0.9
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	0.5	0.6
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	316.5	295.7
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	106.9	113.1
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	209.1	182.0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.5	0.6
Pension Plans, Defined Benefit [Member] | WPL [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	0.3
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	123.1	120.4	122.7
Total plan assets	123.1	120.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8.4	14.0
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	14.0
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	8.4	0
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	32.9	0
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	32.9	0
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	2.8	37.1
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	2.8	37.1
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	2.4	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	2.4	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	2.3	2.4
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	2.3	2.4
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. Mid Cap Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	17.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Mid Cap Core [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	17.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Mid 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. Mid 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. Small Cap Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	4.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Small Cap Core [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	4.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Small 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. Small 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. Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.7	0.6
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	0.7	0.6
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	0.6	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	0.6	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	14.3	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | International - Blend [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14.3	0
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	3.4	3.3
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	1.8	1.7
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	1.6	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	0.8	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	0.8	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	0
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	29.6	0
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	0.8	0
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] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.7	6.1
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	0.7	6.1
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	5.6
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	5.6
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	22.4	25.4
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	21.6
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	3.6	3.8
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	0.1	0.4
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	0.2
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	0.1	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	0.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	123.3	121.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	101.6	98.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21.7	22.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	78.8	74.7	77.5
Total plan assets	78.8	74.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.3	2.1
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	2.1
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	3.3	0
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	24.3	0
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	24.3	0
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	0.8	29.3
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	0.8	29.3
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	0.7	0.8
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	0.7	0.8
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	0.7	0.8
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	0.7	0.8
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. Mid Cap Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	14.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Mid Cap Core [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	14.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | U.S. Mid 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. Mid 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. 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] | 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	0.2	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	0.2	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	0.2	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	10.6	0
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	10.6	0
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	1.0	1.2
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	0.5	0.6
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	0.5	0.6
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	21.5	0
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	21.3	0
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
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] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	4.6
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	0.2	4.6
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	4.1
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	4.1
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	14.9	16.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Fixed Income Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13.9	15.1
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	1.0	1.4
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	0.2
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	0.1
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	0.1
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	78.9	75.0
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	71.8	62.4
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	7.1	12.6
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	22.3	25.1	25.0
Total plan assets	22.3	25.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.9	10.5
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	10.5
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	3.9	0
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	3.1	0
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	3.1	0
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	1.3	1.2
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	1.3	1.2
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	1.2	1.0
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	1.2	1.0
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	1.1	1.0
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	1.1	1.0
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 Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	4.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small Cap Core [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	4.7
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | U.S. Small 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. Small 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. Small Cap Value [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] | 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	0.3	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	0.3	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	0.3	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	1.3	0
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	1.3	0
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	1.6	1.3
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	0.8	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	0.8	0.6
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Developed Markets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | International - Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.4	0.3
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	0.4	0.3
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	3.6	0
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	3.2	0
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	0.4	0
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] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.3	1.1
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	1.1
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	1.0
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	1.0
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	3.5	2.6
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	1.0
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	1.7	1.6
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	0.1
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	0.1
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	22.4	25.3
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	12.2	18.7
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	10.2	6.6
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	(9.1)	(15.3)
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	(3.0)	(5.1)
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	(3.0)	(4.9)
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	(0.2)	(0.6)
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	(0.1)	(0.4)
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	(0.1)	(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	(1.5)	(4.7)
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	(0.5)	(1.6)
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	(0.5)	(1.5)
Defined Benefit Plan Due To Brokers Net [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 Brokers Net [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Accrued Investment Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0.1
Defined Benefit Plan Due To Brokers Net [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ (0.1)

X

- Details

Name:	us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Section 35

-Paragraph 50

-URI http://asc.fasb.org/extlink&oid=6867990&loc=d3e12355-114930



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 87

-Paragraph 49

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph d(iv)(b)(i)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

If aggregate disclosures are presented, the aggregate fair value of plan assets for plans with benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 6

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e2417-114920

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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