Segment Reporting - Selected Financial Data for Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
External revenue
Operating revenues	$ 158,731	$ 151,782	$ 469,370	$ 458,920
Operating expenses:
Selling, general and administrative	27,452	42,199	86,117	125,374
Acquisition, integration and migration expenses	0	1,706	0	9,873
Depreciation and amortization	40,028	42,568	124,632	132,297
Total operating expenses	130,402	142,307	403,118	430,520
Operating income (loss)	28,329	9,475	66,252	28,400
Wireless
External revenue
Operating revenues	114,836	111,266	339,910	338,395
Cable
External revenue
Operating revenues	30,916	29,090	92,610	86,512
Wireline
External revenue
Operating revenues	12,979	11,426	36,850	34,013
Other
External revenue
Operating revenues	0	0	0	0
Intersegment Eliminations
External revenue
Operating revenues	(9,172)	(10,663)	(28,731)	(30,428)
Operating expenses:
Selling, general and administrative	(714)	(736)	(2,043)	(2,114)
Acquisition, integration and migration expenses		0		0
Depreciation and amortization	0	0	0	0
Total operating expenses	(9,172)	(10,663)	(28,731)	(30,428)
Operating income (loss)	0	0	0	0
Intersegment Eliminations | Wireless
External revenue
Operating revenues	(1,263)	(1,239)	(3,746)	(3,707)
Intersegment Eliminations | Cable
External revenue
Operating revenues	(1,266)	(999)	(3,394)	(2,153)
Intersegment Eliminations | Wireline
External revenue
Operating revenues	(6,643)	(8,425)	(21,591)	(24,568)
Intersegment Eliminations | Other
External revenue
Operating revenues	0	0	0	0
Operating Segments
External revenue
Operating revenues	167,903		498,101
Operating Segments | Wireless
External revenue
Operating revenues	116,099	112,505	343,656	342,102
Operating expenses:
Selling, general and administrative	11,191	30,099	35,693	88,201
Acquisition, integration and migration expenses		1,691		9,607
Depreciation and amortization	30,363	32,929	95,853	104,231
Total operating expenses	88,747	105,760	276,786	319,868
Operating income (loss)	27,352	6,745	66,870	22,234
Operating Segments | Cable
External revenue
Operating revenues	32,182	30,089	96,004	88,665
Operating expenses:
Selling, general and administrative	5,331	5,358	14,940	15,083
Acquisition, integration and migration expenses		0		0
Depreciation and amortization	6,102	6,192	18,305	18,070
Total operating expenses	26,348	26,463	78,560	78,205
Operating income (loss)	5,834	3,626	17,444	10,460
Operating Segments | Wireline
External revenue
Operating revenues	19,622	19,851	58,441	58,581
Operating expenses:
Selling, general and administrative	1,780	1,706	5,183	5,065
Acquisition, integration and migration expenses		0		0
Depreciation and amortization	3,435	3,249	10,069	9,536
Total operating expenses	14,500	14,762	43,754	43,010
Operating income (loss)	5,122	5,089	14,687	15,571
Operating Segments | Other
External revenue
Operating revenues	0	0	0	0
Operating expenses:
Selling, general and administrative	9,864	5,772	32,344	19,139
Acquisition, integration and migration expenses		15		266
Depreciation and amortization	128	198	405	460
Total operating expenses	9,979	5,985	32,749	19,865
Operating income (loss)	(9,979)	(5,985)	(32,749)	(19,865)
Service revenue
External revenue
Operating revenues	130,320	139,455	386,003	418,792
Service revenue | Wireless
External revenue
Operating revenues	96,299	107,395	284,154	323,262
Service revenue | Cable
External revenue
Operating revenues	28,578	26,934	85,797	80,229
Service revenue | Wireline
External revenue
Operating revenues	5,443	5,126	16,052	15,301
Service revenue | Other
External revenue
Operating revenues	0	0	0	0
Equipment revenue
External revenue
Operating revenues	15,963	1,994	49,551	8,303
Equipment revenue | Wireless
External revenue
Operating revenues	15,666	1,742	48,859	7,666
Equipment revenue | Cable
External revenue
Operating revenues	234	219	537	547
Equipment revenue | Wireline
External revenue
Operating revenues	63	33	155	90
Equipment revenue | Other
External revenue
Operating revenues	0	0	0	0
Other
External revenue
Operating revenues	12,448	10,333	33,816	31,825
Other | Wireless
External revenue
Operating revenues	2,871	2,129	6,897	7,467
Other | Cable
External revenue
Operating revenues	2,104	1,937	6,276	5,736
Other | Wireline
External revenue
Operating revenues	7,473	6,267	20,643	18,622
Other | Other
External revenue
Operating revenues	0	0	0	0
Cost of services
Operating expenses:
Cost of services	47,886	48,552	146,362	145,744
Cost of services | Intersegment Eliminations
Operating expenses:
Cost of services	(8,458)	(9,927)	(26,688)	(28,314)
Cost of services | Operating Segments | Wireless
Operating expenses:
Cost of services	32,253	33,825	99,491	100,745
Cost of services | Operating Segments | Cable
Operating expenses:
Cost of services	14,837	14,858	45,118	44,956
Cost of services | Operating Segments | Wireline
Operating expenses:
Cost of services	9,266	9,796	28,441	28,357
Cost of services | Operating Segments | Other
Operating expenses:
Cost of services	(12)	0	0	0
Cost of goods sold
Operating expenses:
Cost of services	15,036	7,282	46,007	17,232
Cost of goods sold | Intersegment Eliminations
Operating expenses:
Cost of services	0	0	0	0
Cost of goods sold | Operating Segments | Wireless
Operating expenses:
Cost of services	14,940	7,216	45,749	17,084
Cost of goods sold | Operating Segments | Cable
Operating expenses:
Cost of services	78	55	197	96
Cost of goods sold | Operating Segments | Wireline
Operating expenses:
Cost of services	19	11	61	52
Cost of goods sold | Operating Segments | Other
Operating expenses:
Cost of services	$ (1)	$ 0	$ 0	$ 0