Other Assets - Summary of Other Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Other Assets Noncurrent [Abstract]
Deferred financing costs, Gross Carrying Amount	$ 967	$ 967
Other regulatory assets Deferred financing costs, Gross Carrying Amount	27,761	27,112
Deferred costs recoverable in future years, Gross Carrying Amount	23,793	23,793
Other regulatory assets, Net Gross Carrying Amount	51,554	50,905
Investments, Gross Carrying Amount	2,519	2,519
Other assets, Gross Carrying Amount	55,040	54,391
Deferred financing costs, Accumulated Amortization	(253)	(204)
Other regulatory assets Deferred financing costs, Accumulated Amortization	(14,154)	(13,208)
Other regulatory assets, Net Accumulated Amortization	(14,154)	(13,208)
Other assets, Accumulated Amortization	(14,407)	(13,412)
Deferred financing costs, Net Carrying Amount	714	763
Other regulatory assets Deferred financing costs, Net Carrying Amount	13,607	13,904
Deferred costs recoverable in future years, Net Carrying Amount	23,793	23,793
Other regulatory assets, Net Carrying Amount	37,400	37,697
Investments, Net Carrying Amount	2,519	2,519
Other assets, Net Carrying Amount	$ 40,633	$ 40,979