Supplemental Cash Flow Information -Supplemental Cash Flow Information and Non-cash Investing and Financing Activities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Supplemental cash flow information
Cash paid during the period for interest	$ 7,081us-gaap_InterestPaid	$ 7,330us-gaap_InterestPaid
Cash paid during the period for taxes		75us-gaap_IncomeTaxesPaidNet
Non-cash investing and financing activities
Non-cash right of way additions to electric plant		337
Change in accrued additions to electric plant	12,106	30,039
Allowance for funds used during construction - debt	408	396
Non-cash members' contributions		91us-gaap_ContributionOfProperty
Net non-cash equity issuances related to the Merger and Reorganization	97,193us-gaap_NoncashMergerRelatedCosts
Net non-cash noncontrolling equity issuances related to the Merger and Reorganization	119,607
Non-cash noncontrolling interests contributions		27
Non-cash noncontrolling interests equity issuance	755	2,467
Dividends payable	6,099us-gaap_PaymentsOfDividends
Distribution payable to noncontrolling interest	$ 2,384

Change in accrued additions to electric plant.

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Non cash contributions from noncontrolling interests.

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Non cash distribution payable to minority interest.

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Non cash noncontrolling interest equity issuance.

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Noncash or part noncash merger noncash financial or equity instrument consideration.

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Cash inflow due to change during the period in the allowance for other funds used during construction classified as an investing activity.

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Value of property contributed in noncash investing and financing activities.

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The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

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The amount of cash paid for interest during the period.

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Amount of expense (income) related to the increase (decrease) in reserve for business combination costs. Includes, but is not limited to, legal, accounting, and other costs incurred to consummate the merger.

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The amount of fixed assets that an Entity acquires in a noncash (or part noncash) acquisition. Noncash is defined as information about all investing and financing activities of an enterprise during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests.

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