v2.4.0.6
Consolidated Statements Of Cash Flows (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Cash flows from operating activities:      
Net income $ 335.7 $ 321.9 $ 306.3
Adjustments to reconcile net income to net cash flows from operating activities:      
Depreciation and amortization 332.9 323.8 292.3
Other amortizations 55.0 56.3 51.8
Deferred tax expense (benefit) and investment tax credits 143.3 10.2 216.6
Equity income from unconsolidated investments, net (41.3) (39.3) (38.1)
Distributions from equity method investments 34.2 32.3 32.2
Equity component of allowance for funds used during construction (14.1) (7.6) (11.2)
Non-cash valuation and regulatory-related charges 3.3 25.5 38.0
Other (2.6) (5.2) (4.7)
Other changes in assets and liabilities:      
Accounts receivable 61.3 (54.3) 16.3
Sales of accounts receivable (10.0) 75.0 65.0
Income tax refunds receivable 20.9 0.3 130.4
Regulatory assets (178.1) (413.1) (20.8)
Regulatory liabilities 16.4 168.3 8.4
Derivative liabilities (37.6) 10.7 (52.0)
Non-current taxes payable (2.9) (5.1) (66.6)
Pension and other benefit obligations 51.3 8.9 (20.1)
Other (14.2) 45.6 12.2
Net cash flows from operating activities 841.1 702.7 984.9
Cash flows from (used for) investing activities:      
Utility business - Riverside Energy Center (403.5) 0 0
Utility business - other (622.0) (608.1) (833.3)
Alliant Energy Corporate Services, Inc. and non-regulated businesses (132.6) (65.3) (33.6)
Advances for customer energy efficiency projects (0.4) (5.1) (17.1)
Collections of advances for customer energy efficiency projects 22.9 31.0 34.2
Other (19.9) (4.6) (16.7)
Net cash flows from (used for) investing activities (1,155.5) (652.1) (866.5)
Cash flows from (used for) financing activities:      
Common stock dividends (199.3) (188.1) (174.6)
Preferred dividends paid by subsidiaries (15.9) (16.8) (18.7)
Payments to redeem cumulative preferred stock 0 (40.0) 0
Proceeds from issuance of long-term debt 385.0 0.4 500.0
Payments to retire long-term debt (1.4) (1.3) (307.8)
Net change in commercial paper 164.7 55.4 (142.6)
Other (8.9) (8.1) 9.3
Net cash flows from (used for) financing activities 324.2 (198.5) (134.4)
Net increase (decrease) in cash and cash equivalents 9.8 (147.9) (16.0)
Cash and cash equivalents at beginning of period 11.4 159.3 175.3
Cash and cash equivalents at end of period 21.2 11.4 159.3
Supplemental cash flows information:      
Interest, net of capitalized interest 155.2 157.6 165.5
Income taxes, net of refunds (20.3) (10.8) (116.2)
Significant non-cash investing and financing activities:      
Accrued capital expenditures 105.3 49.7 75.0
Deferred income tax liabilities [Member]
      
Other changes in assets and liabilities:      
Deferred income taxes 87.6 148.5 28.9
IPL [Member]
      
Cash flows from operating activities:      
Net income 150.2 139.3 143.4
Adjustments to reconcile net income to net cash flows from operating activities:      
Depreciation and amortization 188.9 179.1 177.0
Deferred tax expense (benefit) and investment tax credits 19.3 (58.6) 116.0
Equity component of allowance for funds used during construction (5.2) (3.5) (3.0)
Non-cash valuation and regulatory-related charges 3.0 14.8 30.5
Other 7.6 8.7 3.7
Other changes in assets and liabilities:      
Accounts receivable (0.7) 22.4 5.1
Sales of accounts receivable (10.0) 75.0 65.0
Income tax refunds receivable 13.5 (9.3) 84.3
Production fuel (7.5) 12.4 21.0
Regulatory assets (129.0) (328.8) (49.5)
Regulatory liabilities (12.1) 156.3 17.5
Derivative liabilities (17.5) 9.6 (29.0)
Non-current taxes payable (2.8) (4.8) (28.4)
Pension and other benefit obligations 21.0 (8.3) (9.0)
Other (6.3) 16.7 (37.0)
Net cash flows from operating activities 291.0 366.9 549.6
Cash flows from (used for) investing activities:      
Utility business - other (307.5) (293.7) (382.8)
Proceeds from sale of wind project assets to affiliate 0 115.3 0
Other (23.7) (22.2) (32.2)
Net cash flows from (used for) investing activities (331.2) (200.6) (415.0)
Cash flows from (used for) financing activities:      
Common stock dividends (122.9) (73.4) 0
Preferred dividends paid by subsidiaries (12.6) (13.5) (15.4)
Capital contributions from parent 110.0 54.0 50.0
Repayment of capital to parent 0 (100.7) (118.2)
Payments to redeem cumulative preferred stock 0 (40.0) 0
Proceeds from issuance of long-term debt 0 0 350.0
Payments to retire long-term debt 0 0 (206.3)
Net change in commercial paper 69.2 7.1 (190.0)
Other (1.1) (3.4) 0.6
Net cash flows from (used for) financing activities 42.6 (169.9) (129.3)
Net increase (decrease) in cash and cash equivalents 2.4 (3.6) 5.3
Cash and cash equivalents at beginning of period 2.1 5.7 0.4
Cash and cash equivalents at end of period 4.5 2.1 5.7
Supplemental cash flows information:      
Interest, net of capitalized interest 78.3 78.0 82.0
Income taxes, net of refunds 3.3 25.3 (125.9)
Significant non-cash investing and financing activities:      
Accrued capital expenditures 53.4 23.9 45.7
IPL [Member] | Deferred income tax liabilities [Member]
      
Other changes in assets and liabilities:      
Deferred income taxes 78.6 145.9 42.0
WPL [Member]
      
Cash flows from operating activities:      
Net income 165.7 163.5 152.3
Adjustments to reconcile net income to net cash flows from operating activities:      
Depreciation and amortization 140.9 140.1 108.6
Other amortizations 43.7 42.4 39.5
Deferred tax expense (benefit) and investment tax credits 88.6 93.7 98.5
Equity income from unconsolidated investments, net (42.1) (38.7) (37.8)
Distributions from equity method investments 34.2 32.3 32.2
Equity component of allowance for funds used during construction (8.9) (4.1) (8.2)
Non-cash valuation and regulatory-related charges (2.9) 10.8 0
Other changes in assets and liabilities:      
Accounts receivable (11.0) 9.8 4.6
Income tax refunds receivable (2.9) 39.9 40.7
Regulatory assets (49.1) (84.3) 28.7
Regulatory liabilities 28.5 12.0 (9.1)
Derivative liabilities (20.1) 1.1 (23.0)
Non-current taxes payable (0.1) (0.3) (38.5)
Pension and other benefit obligations 31.7 8.8 (2.5)
Other 31.2 1.8 (13.6)
Net cash flows from operating activities 427.4 428.8 372.4
Cash flows from (used for) investing activities:      
Utility business - Riverside Energy Center (403.5) 0 0
Utility business - other (314.5) (314.4) (450.5)
Advances for customer energy efficiency projects (0.4) (5.1) (16.0)
Collections of advances for customer energy efficiency projects 20.9 26.8 30.3
Other (12.7) (12.7) (13.1)
Net cash flows from (used for) investing activities (710.2) (305.4) (449.3)
Cash flows from (used for) financing activities:      
Common stock dividends (112.0) (112.1) (109.5)
Preferred dividends paid by subsidiaries (3.3) (3.3) (3.3)
Capital contributions from parent 90.0 25.0 75.0
Repayment of capital to parent 0 0 0
Proceeds from issuance of long-term debt 250.0 0 150.0
Payments to retire long-term debt 0 0 (100.0)
Net change in commercial paper 60.9 (21.7) 47.4
Other (4.8) (8.7) (1.1)
Net cash flows from (used for) financing activities 280.8 (120.8) 58.5
Net increase (decrease) in cash and cash equivalents (2.0) 2.6 (18.4)
Cash and cash equivalents at beginning of period 2.7 0.1 18.5
Cash and cash equivalents at end of period 0.7 2.7 0.1
Supplemental cash flows information:      
Interest, net of capitalized interest 79.5 79.9 80.9
Income taxes, net of refunds (3.3) (51.3) (3.8)
Significant non-cash investing and financing activities:      
Accrued capital expenditures $ 39.5 $ 19.7 $ 27.4