Segment Information - Operating Income Reconciliation (Details) - USD ($) $ 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
Reconciliation of total operating income to the consolidated statement of income
Operating income	$ 3,700	$ 3,703	$ 6,889	$ 4,500	$ 3,888	$ 4,195	$ 5,260	$ 5,919	$ 18,792	$ 19,262	$ 30,471
Income before income tax provision									1,697	2,457	14,009
Tele-communications
Reconciliation of total operating income to the consolidated statement of income
Operating income									19,526	20,161	30,683
Operating segment
Reconciliation of total operating income to the consolidated statement of income
Operating income									18,792	19,262	30,471
Corporate other expense									17,095	16,805	16,462
Income before income tax provision									$ 1,697	$ 2,457	$ 14,009