v2.4.0.6
Consolidated Statements Of Income (USD $)
In Millions, except Share data in Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Utility:      
Electric $ 2,589.3 $ 2,635.8 $ 2,674.2
Gas 396.3 476.7 480.6
Other 56.7 62.0 64.6
Non-regulated 52.2 46.9 42.7
Total operating revenues 3,094.5 3,221.4 3,262.1
Utility:      
Electric production fuel and energy purchases 712.3 764.5 819.2
Purchased electric capacity 271.5 257.2 279.7
Electric transmission service 341.3 323.8 279.5
Cost of gas sold 217.2 295.2 304.0
Other operation and maintenance 590.0 630.2 617.2
Non-regulated operation and maintenance 11.9 18.0 19.4
Depreciation and amortization 332.4 321.0 287.3
Taxes other than income taxes 98.2 98.2 95.8
Total operating expenses 2,574.8 2,708.1 2,702.1
Operating income 519.7 513.3 560.0
Interest expense and other:      
Interest expense 156.7 158.3 162.8
Equity income from unconsolidated investments, net (41.3) (39.3) (38.1)
Allowance for funds used during construction (21.9) (12.0) (18.0)
Interest income and other (4.0) (4.3) (4.6)
Total interest expense and other 89.5 102.7 102.1
Income from continuing operations before income taxes 430.2 410.6 457.9
Income tax expense (benefit) 89.4 69.2 147.7
Income from continuing operations, net of tax 340.8 341.4 310.2
Loss from discontinued operations, net of tax (5.1) (19.5) (3.9)
Net income 335.7 321.9 306.3
Preferred dividend requirements of subsidiaries 15.9 18.3 18.7
Net income attributable to common shareowners 319.8 303.6 287.6
Weighted average number of common shares outstanding (basic) (000s) (in shares) 110,753 110,626 110,442
Weighted average number of common shares outstanding (diluted) (000s) (in shares) 110,768 110,678 110,521
Earnings per weighted average common share attributable to Alliant Energy common shareowners (basic and diluted):      
Income from continuing operations, net of tax (in dollars per share) $ 2.93 $ 2.92 $ 2.64
Loss from discontinued operations, net of tax (in dollars per share) $ (0.04) $ (0.18) $ (0.04)
Net income (in dollars per share) $ 2.89 $ 2.74 $ 2.60
Amounts attributable to common shareowners:      
Income from continuing operations, net of tax 324.9 323.1 291.5
Loss from discontinued operations, net of tax (5.1) (19.5) (3.9)
Net income attributable to common shareowners 319.8 303.6 287.6
Dividends declared per common share (in dollars per share) $ 1.80 $ 1.70 $ 1.58
IPL [Member]
      
Utility:      
Electric 1,371.1 1,408.3 1,464.3
Gas 226.7 276.3 274.3
Other 52.5 55.5 57.2
Total operating revenues 1,650.3 1,740.1 1,795.8
Utility:      
Electric production fuel and energy purchases 344.5 383.1 418.0
Purchased electric capacity 153.7 147.7 145.0
Electric transmission service 235.0 219.2 179.1
Cost of gas sold 124.9 175.6 178.7
Other operation and maintenance 350.0 375.0 384.5
Depreciation and amortization 188.9 179.1 177.0
Taxes other than income taxes 53.0 52.0 51.6
Total operating expenses 1,450.0 1,531.7 1,533.9
Operating income 200.3 208.4 261.9
Interest expense and other:      
Interest expense 78.5 78.7 82.2
Allowance for funds used during construction (8.4) (5.8) (5.5)
Interest income and other (0.2) (0.2) (0.5)
Total interest expense and other 69.9 72.7 76.2
Income from continuing operations before income taxes 130.4 135.7 185.7
Income tax expense (benefit) (19.8) (3.6) 42.3
Net income 150.2 139.3 143.4
Preferred dividend requirements of subsidiaries 12.6 15.0 15.4
Net income attributable to common shareowners 137.6 124.3 128.0
Amounts attributable to common shareowners:      
Net income attributable to common shareowners 137.6 124.3 128.0
WPL [Member]
      
Utility:      
Electric 1,218.2 1,227.5 1,209.9
Gas 169.6 200.4 206.3
Other 4.2 6.5 7.4
Total operating revenues 1,392.0 1,434.4 1,423.6
Utility:      
Electric production fuel and energy purchases 367.8 381.4 401.2
Purchased electric capacity 117.8 109.5 134.7
Electric transmission service 106.3 104.6 100.4
Cost of gas sold 92.3 119.6 125.3
Other operation and maintenance 240.0 255.2 232.7
Depreciation and amortization 140.9 140.1 108.6
Taxes other than income taxes 42.1 43.6 41.9
Total operating expenses 1,107.2 1,154.0 1,144.8
Operating income 284.8 280.4 278.8
Interest expense and other:      
Interest expense 80.2 79.9 78.6
Equity income from unconsolidated investments, net (42.1) (38.7) (37.8)
Allowance for funds used during construction (13.5) (6.2) (12.5)
Interest income and other (0.1) 0 (0.1)
Total interest expense and other 24.5 35.0 28.2
Income from continuing operations before income taxes 260.3 245.4 250.6
Income tax expense (benefit) 94.6 81.9 98.3
Net income 165.7 163.5 152.3
Preferred dividend requirements of subsidiaries 3.3 3.3 3.3
Net income attributable to common shareowners 162.4 160.2 149.0
Amounts attributable to common shareowners:      
Net income attributable to common shareowners $ 162.4 $ 160.2 $ 149.0