Segment Information (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of total operating income to the consolidated statement of income
Operating income	$ 3,888	$ 4,195	$ 5,260	$ 5,919	$ 7,821	$ 6,620	$ 7,892	$ 8,138	$ 19,262	$ 30,471	$ 41,771
Income before income tax provision									2,457	14,009	19,270
Telecommunications
Reconciliation of total operating income to the consolidated statement of income
Operating income									20,161	30,683	41,907
Gain from the sale of property											6,500
Parent Company
Reconciliation of total operating income to the consolidated statement of income
Income before income tax provision									1,100	8,099	10,488
Operating segment
Reconciliation of total operating income to the consolidated statement of income
Operating income									19,262	30,471	41,771
Corporate other expense									(16,805)	(16,462)	(22,501)
Income before income tax provision									$ 2,457	$ 14,009	$ 19,270