Income Taxes (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating Loss Carryforwards [Line Items]
Decrease in accrued taxes	$ (2,389)	$ (2,431)
Tax Year 2014 [Member]
Operating Loss Carryforwards [Line Items]
Net reduction in taxes due to the federal government	17,600
Reserve against tangible property deductions	2,300
Net operating loss carry-forward	7,800
Income tax refund receivable	10,300
Current income tax refund receivable	500
Increase in regulatory assets	1,500
Decrease in accrued taxes	5,000
Increase in accumulated deferred income taxes	$ 16,800