Acquisitions (Details) - DTE Electric $ in Millions	Oct. 01, 2015 USD ($) MW	Jan. 21, 2015 USD ($) MW
Natural Gas Facility in Carson City Michigan
Business Acquisition [Line Items]
Gas facility capacity, MW		732
Total purchase price \| $		$ 241
Subsequent event \| Natural Gas Facility in East China Township Michigan
Business Acquisition [Line Items]
Gas facility capacity, MW	350
Total purchase price \| $	$ 69

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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