CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME [Abstract]
Operating revenues	$ 326,946	$ 308,942	$ 288,075
Operating expenses
Cost of goods and services, exclusive of depreciation and amortization shown separately below	129,743	125,140	117,407
Impairment charge on goodwill	0	0	10,952
Selling, general and administrative, exclusive of depreciation and amortization shown below	69,370	67,673	60,646
Depreciation and amortization	65,890	60,722	64,412
Total operating expenses	265,003	253,535	253,417
Operating income	61,943	55,407	34,658
Other income (expense)
Interest expense	(8,148)	(8,468)	(7,850)
Gain on investments, net	208	756	858
Non-operating income, net	2,031	1,769	945
Income from continuing operations before income taxes	56,034	49,464	28,611
Income tax expense	22,151	19,878	12,008
Net income from continuing operations	33,883	29,586	16,603
Loss from discontinued operations of Converged Services, net of tax benefits of $0, $0 and $196, respectively	0	0	(300)
Net income	33,883	29,586	16,303
Other comprehensive income (loss):
Unrealized gain (loss) on interest rate hedge, net of tax	(1,472)	3,457	(863)
Comprehensive income	$ 32,411	$ 33,043	$ 15,440
Net income per share, basic:
Net income from continuing operations (in dollars per share)	$ 1.41	$ 1.23	$ 0.69
Loss from discontinued operations, net of income taxes (in dollars per share)	$ 0	$ 0	$ (0.01)
Net income (in dollars per share)	$ 1.41	$ 1.23	$ 0.68
Net income per share, diluted:
Net income from continuing operations (in dollars per share)	$ 1.39	$ 1.23	$ 0.69
Loss from discontinued operations, net of income taxes (in dollars per share)	$ 0	$ 0	$ (0.01)
Net income (in dollars per share)	$ 1.39	$ 1.23	$ 0.68
Weighted average shares outstanding, basic (in shares)	24,099	24,001	23,877
Weighted average shares outstanding, diluted (in shares)	24,360	24,115	24,019