Segment Reporting - Selected Financial Data for Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
External revenues [Abstract]
Service revenues	$ 123,538	$ 139,645
Equipment revenues	17,579	3,359
Equipment revenues	10,615	10,876
Total operating revenues	151,732	153,880
Operating expenses:
Costs of services	49,342	48,776
Cost of goods sold	15,805	4,985
Selling, general & administrative	28,750	40,153
Acquisition, integration & migration expenses	0	4,489
Depreciation & amortization	43,487	44,804
Total operating expenses	137,384	143,207
Operating income (loss)	14,348	10,673
Wireless
External revenues [Abstract]
Service revenues	89,759	108,186
Equipment revenues	17,374	3,145
Equipment revenues	2,026	2,897
Total operating revenues	109,159	114,228
Cable
External revenues [Abstract]
Service revenues	28,471	26,411
Equipment revenues	159	182
Equipment revenues	2,050	1,853
Total operating revenues	30,680	28,446
Wireline
External revenues [Abstract]
Service revenues	5,308	5,048
Equipment revenues	46	32
Equipment revenues	6,539	6,126
Total operating revenues	11,893	11,206
Other
External revenues [Abstract]
Service revenues	0	0
Equipment revenues	0	0
Equipment revenues	0	0
Total operating revenues	0	0
Operating Segments | Wireless
External revenues [Abstract]
Total operating revenues	110,398	115,463
Operating expenses:
Costs of services	33,750	33,423
Cost of goods sold	15,727	4,895
Selling, general & administrative	12,135	28,464
Acquisition, integration & migration expenses	0	3,792
Depreciation & amortization	33,925	35,752
Total operating expenses	95,537	106,326
Operating income (loss)	14,861	9,137
Operating Segments | Cable
External revenues [Abstract]
Total operating revenues	31,711	29,013
Operating expenses:
Costs of services	15,156	15,178
Cost of goods sold	56	50
Selling, general & administrative	4,948	4,858
Acquisition, integration & migration expenses	0	0
Depreciation & amortization	6,024	5,788
Total operating expenses	26,184	25,874
Operating income (loss)	5,527	3,139
Operating Segments | Wireline
External revenues [Abstract]
Total operating revenues	19,707	19,154
Operating expenses:
Costs of services	9,802	9,233
Cost of goods sold	22	40
Selling, general & administrative	1,717	1,676
Acquisition, integration & migration expenses	0	0
Depreciation & amortization	3,394	3,132
Total operating expenses	14,935	14,081
Operating income (loss)	4,772	5,073
Operating Segments | Other
External revenues [Abstract]
Total operating revenues	0	0
Operating expenses:
Costs of services	0	0
Cost of goods sold	0	0
Selling, general & administrative	10,668	5,847
Acquisition, integration & migration expenses	0	697
Depreciation & amortization	144	132
Total operating expenses	10,812	6,676
Operating income (loss)	(10,812)	(6,676)
Intersegment Eliminations
External revenues [Abstract]
Total operating revenues	(10,084)	(9,750)
Operating expenses:
Costs of services	(9,366)	(9,058)
Cost of goods sold	0	0
Selling, general & administrative	(718)	(692)
Acquisition, integration & migration expenses	0	0
Depreciation & amortization	0	0
Total operating expenses	(10,084)	(9,750)
Operating income (loss)	0	0
Intersegment Eliminations | Wireless
External revenues [Abstract]
Total operating revenues	1,239	1,235
Intersegment Eliminations | Cable
External revenues [Abstract]
Total operating revenues	1,031	567
Intersegment Eliminations | Wireline
External revenues [Abstract]
Total operating revenues	7,814	7,948
Intersegment Eliminations | Other
External revenues [Abstract]
Total operating revenues	$ 0	$ 0