Commitments and Contingencies, Purchased Power Agreements (Details) - Independent Power Producing Entities	3 Months Ended
Mar. 31, 2017 MW
Purchased Power Agreements [Abstract]
Generating capacity under long term purchased power agreements (in MW)	1,571
Purchase Power Agreement Expiration (year)	2032

The expiration of purchase power agreements currently under contract (year).

No definition available.

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Data Type:	us-types:durationStringItemType
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