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Schedule I - Statements of Comprehensive Income (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Statements of comprehensive income |  |  |  |  |  |  |  |  |  |  |
Net income attributed to common shareholders | $ 432.6 | $ 215.4 | $ 199.1 | $ 356.6 | $ 194.4 | $ 217.0 | $ 181.4 | $ 346.2 | $ 1,203.7 | $ 939.0 | $ 638.5
Derivatives accounted for as cash flow hedges |  |  |  |  |  |  |  |  |  |  |
Gains on settlement, net of tax of $7.6 |  |  |  |  |  |  |  |  | 0.0 | 0.0 | 11.4
Reclassification of gains to net income, net of tax |  |  |  |  |  |  |  |  | (1.3) | (1.3) | (0.8)
Cash flow hedges, net |  |  |  |  |  |  |  |  | (1.3) | (1.3) | 10.6
Defined benefit plans |  |  |  |  |  |  |  |  |  |  |
Pension and OPEB costs arising during the period, net of tax |  |  |  |  |  |  |  |  | 0.9 | (0.8) | (6.3)
Amortization of pension and OPEB costs included in net periodic benefit cost, net of tax |  |  |  |  |  |  |  |  | 0.4 | 0.4 | 0.0
Defined benefit plans, net |  |  |  |  |  |  |  |  | 1.3 | (0.4) | (6.3)
Other comprehensive (loss) income, net of tax |  |  |  |  |  |  |  |  | 0.0 | (1.7) | 4.3
Comprehensive income attributed to common shareholders |  |  |  |  |  |  |  |  | 1,203.7 | 937.3 | 642.8
Other comprehensive (loss) income, tax |  |  |  |  |  |  |  |  |  |  |
Gains on settlement, tax |  |  |  |  |  |  |  |  |  |  | 7.6
WEC Energy Group |  |  |  |  |  |  |  |  |  |  |
Statements of comprehensive income |  |  |  |  |  |  |  |  |  |  |
Net income attributed to common shareholders |  |  |  |  |  |  |  |  | 1,203.7 | 939.0 | 638.5
Derivatives accounted for as cash flow hedges |  |  |  |  |  |  |  |  |  |  |
Gains on settlement, net of tax of $7.6 |  |  |  |  |  |  |  |  | 0.0 | 0.0 | 11.4
Reclassification of gains to net income, net of tax |  |  |  |  |  |  |  |  | (1.3) | (1.3) | (0.8)
Cash flow hedges, net |  |  |  |  |  |  |  |  | (1.3) | (1.3) | 10.6
Defined benefit plans |  |  |  |  |  |  |  |  |  |  |
Pension and OPEB costs arising during the period, net of tax |  |  |  |  |  |  |  |  | (0.1) | (1.0) | (1.5)
Amortization of pension and OPEB costs included in net periodic benefit cost, net of tax |  |  |  |  |  |  |  |  | 0.2 | 0.3 | 0.0
Defined benefit plans, net |  |  |  |  |  |  |  |  | 0.1 | (0.7) | (1.5)
Other comprehensive income (loss) from subsidiaries, net of tax |  |  |  |  |  |  |  |  | 1.2 | 0.3 | (4.8)
Other comprehensive (loss) income, net of tax |  |  |  |  |  |  |  |  | 0.0 | (1.7) | 4.3
Comprehensive income attributed to common shareholders |  |  |  |  |  |  |  |  | $ 1,203.7 | $ 937.3 | 642.8
Other comprehensive (loss) income, tax |  |  |  |  |  |  |  |  |  |  |
Gains on settlement, tax |  |  |  |  |  |  |  |  |  |  | $ 7.6

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