Property Plant and Equipment Property Plant and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 8,938.4	$ 8,075.0
Accumulated Depreciation	2,306.8	2,128.6
Property, plant and equipment, net	6,631.6	5,946.4
Electric plant
Property, Plant and Equipment [Line Items]
Property, plant and equipment	8,453.0	7,227.7
CWIP
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 485.4	$ 847.3

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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