PROPERTY, PLANT, AND EQUIPMENT - Balances (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Property, plant, and equipment
Accumulated depreciation	$ 1,808.4	$ 1,750.7
Net property, plant, and equipment	5,098.6	4,885.9
Regulated operations
Property, plant, and equipment
Accumulated depreciation	1,808.4	1,750.7
Net	5,003.6	4,650.9
CWIP	95.0	235.0
Net property, plant, and equipment	5,098.6	4,885.9
Electric - generation \| Regulated operations
Property, plant, and equipment
Property, plant, and equipment	2,816.7	2,981.5
Electric - distribution \| Regulated operations
Property, plant, and equipment
Property, plant, and equipment	2,076.3	1,921.2
Natural gas - distribution, storage, and transmission \| Regulated operations
Property, plant, and equipment
Property, plant, and equipment	1,159.5	1,064.1
Property, plant, and equipment to be retired, net \| Regulated operations
Property, plant, and equipment
Property, plant, and equipment to be retired, net	277.0	0.0
Other \| Regulated operations
Property, plant, and equipment
Property, plant, and equipment	482.5	$ 434.8
Columbia Energy Center Unit 1
Property, plant, and equipment
Net book value of plant to be retired	89.1
Columbia Energy Center Unit 2
Property, plant, and equipment
Net book value of plant to be retired	$ 187.9

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 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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