Supplemental Cash Flow Information - Supplemental Cash Flow Information and Non-cash Investing and Financing Activities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Supplemental cash flow information
Cash paid during the period for interest	$ 20,022	$ 22,367
Cash paid during the period for taxes		75
Non-cash investing and financing activities
Non-cash right of way additions to electric plant		337
Change in accrued additions to electric plant	4,387	31,421
Allowance for funds used during construction - debt	1,312	1,197
Net non-cash equity issuances related to the Merger and Reorganization	97,193
Net non-cash noncontrolling equity issuances related to the Merger and Reorganization	119,607
Non-cash noncontrolling interests equity issuance	755	$ 4,590
Dividends and distributions payable	$ 13,634		$ 14,130