Plant, Property, and Equipment (Jointly Owned Regulated Utility Facilities) (Details) $ in Millions	Dec. 31, 2015 USD ($)
J.H. Campbell Unit 3 [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Ownership share	93.30%
Utility plant in service	$ 1,078
Accumulated depreciation	(542)
Construction work-in-progress	494
Net investment	$ 1,030
Ludington [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Ownership share	51.00%
Utility plant in service	$ 245
Accumulated depreciation	(151)
Construction work-in-progress	157
Net investment	251
Distribution [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Utility plant in service	200
Accumulated depreciation	(63)
Construction work-in-progress	4
Net investment	$ 141

The period end amount owned by the reporting utility of a jointly owned utility plant in service.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 360
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 10.C)
-URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 10
-Section C

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- Definition

The total period end amount of plant in service and construction in progress net of accumulated depreciation for the utility's share of jointly owned electricity generation plant.

+ References

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- Definition

The period end amount of construction work in progress at a jointly owned electricity generation plant.

+ References

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- Definition

The period end amount of accumulated depreciation in a jointly owned electricity generation plant.

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- Definition

The proportionate share of interest (percent) in a jointly owned utility plant.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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