Electric Plant and Depreciation - Additional Information (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Public Utilities Property Plant And Equipment [Abstract]
Electric plant, net includes plant acquisition adjustments	$ 27.7	$ 28.6

Amount of acquisition adjustments included in property, plant and equipment (PPE) for utilities.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant