Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating revenues	$ 96,780	$ 97,848	$ 99,541	$ 98,794	$ 99,207	$ 100,905	$ 96,187	$ 97,114	$ 392,963	$ 393,413	$ 390,739
Operating income	3,700	3,703	6,889	4,500	3,888	4,195	5,260	5,919	18,792	19,262	30,471
Net income (loss)	$ (214)	$ (279)	$ 1,445	$ 154	$ (435)	$ 105	$ 455	$ 975	$ 1,106	$ 1,100	$ 8,099
Earnings (Loss) per share - basic (in dollars per share)	$ (0.020)	$ (0.020)	$ 0.130	$ 0.010	$ (0.040)	$ 0.010	$ 0.040	$ 0.090	$ 0.10	$ 0.10	$ 0.76
Earnings (Loss) per share - diluted (in dollars per share)	$ (0.020)	$ (0.020)	$ 0.130	$ 0.010	$ (0.040)	$ 0.010	$ 0.040	$ 0.090	$ 0.10	$ 0.10	$ 0.72
Pension settlement losses	$ 800	$ 500			$ 1,700	$ 4,100	$ 1,400	$ 900
Connect America Fund Phase II
Operating revenues						$ 2,200