Near-term repairs, maintenance and capital improvements to restore the power plant to full capacity

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Osprey Energy Center Agreement Term

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Acquisition (Details) $ in Millions	3 Months Ended	6 Months Ended
Acquisition (Details) $ in Millions	Dec. 31, 2014 USD ($)	Jun. 30, 2016 USD ($)	Apr. 01, 2016 USD ($) MW	Feb. 05, 2016 USD ($) MW	Oct. 01, 2015 USD ($)
Granite Ridge Energy Center [Member]
Business Acquisition [Line Items]
Business combination, recognized identifiable assets acquired and liabilities assumed, net				$ 500
Power generation capacity \| MW				745
Summer Peaking Capacity \| MW				695
Crane Champion Holdco, LLC [Member]
Business Acquisition [Line Items]
Ownership percentage of acquiree					75.00%
EDF Trading North America, LLC [Member]
Business Acquisition [Line Items]
Ownership percentage of acquiree					25.00%
Champion Energy Marketing, LLC [Member]
Business Acquisition [Line Items]
Business combination, recognized identifiable assets acquired and liabilities assumed, net					$ 240
South Point Energy Center [Member]
Business Acquisition [Line Items]
Proceeds from Sale of Productive Assets		$ 76
Net present value of transmission capacity payment obligations			$ 112
Remaining tribal lease costs			9
Near-term repairs, maintenance and capital improvements to restore the power plant to full capacity			$ 21
Summer Peaking Capacity \| MW			504
Osprey Energy Center [Member]
Business Acquisition [Line Items]
Proceeds from Sale of Productive Assets	$ 166
Osprey Energy Center Agreement Term	27 months