A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

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- Definition

The portion of the difference between total income tax expense or benefit as reported in the Income Statement and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to changes in the income tax rates under enacted tax laws in the period.

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INCOME TAXES (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income taxes
Effective tax rate (as a percent)	31.40%	28.50%	36.30%	32.20%
Federal statutory tax rate (as a percent)	35.00%	35.00%	35.00%	35.00%
Decrease in provision for income taxes related to effective settlement and remeasurement of uncertain tax positions				$ 6.2
Decrease in liability for unrecognized tax benefits			7.7
WPS
Income taxes
Authorized recovery of income tax amounts previously expensed related to the Federal Health Care Reform Act		5.9		5.9
PGL and NSG
Income taxes
Reversal of regulatory liability related to Illinois income tax rate changes	$ 3.7