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Operations and Significant Accounting Policies - Reclassification of Prior Income Statement (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Operating Revenue – Utility [Member]
Schedule of Prior Period Reclassification Adjustments [Line Items]
Prior Period Reclassification Adjustment	$ 1,007.7	$ 991.2
Operating Revenue – Non-utility [Member]
Schedule of Prior Period Reclassification Adjustments [Line Items]
Prior Period Reclassification Adjustment	339.0	495.2
Fuel, Purchased Power and Gas – Utility [Member]
Schedule of Prior Period Reclassification Adjustments [Line Items]
Prior Period Reclassification Adjustment	$ 7.0	$ 7.9

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- Definition

[Line Items] for Schedule of prior period reclassification adjustments to conform the presentation of prior period financial statements with the presentation in the current period.

+ References

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- Definition

The amount of a reclassification adjustment made to prior period financial statement amounts.

+ References

No definition available.

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