Revenue from Contracts with Customers - Revenue by Category (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 158,731	$ 151,782	$ 469,370	$ 458,920
Wireless
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	114,836	111,266	339,910	338,395
Cable
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	30,916	29,090	92,610	86,512
Wireline
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	12,979	11,426	36,850	34,013
Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	167,903		498,101
Operating Segments | Wireless service
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	96,299		284,154
Operating Segments | Equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	15,963		49,551
Operating Segments | Business, residential and enterprise
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	40,036		119,837
Operating Segments | Tower and other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	15,605		44,559
Operating Segments | Wireless
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	116,099	112,505	343,656	342,102
Operating Segments | Wireless | Wireless service
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	96,299		284,154
Operating Segments | Wireless | Equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	15,666		48,859
Operating Segments | Wireless | Business, residential and enterprise
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Wireless | Tower and other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	4,134		10,643
Operating Segments | Cable
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	32,182	30,089	96,004	88,665
Operating Segments | Cable | Wireless service
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Cable | Equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	234		537
Operating Segments | Cable | Business, residential and enterprise
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	29,334		87,931
Operating Segments | Cable | Tower and other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2,614		7,536
Operating Segments | Wireline
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	19,622	19,851	58,441	58,581
Operating Segments | Wireline | Wireless service
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Wireline | Equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	63		155
Operating Segments | Wireline | Business, residential and enterprise
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	10,702		31,906
Operating Segments | Wireline | Tower and other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	8,857		26,380
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(9,172)	(10,663)	(28,731)	(30,428)
Intersegment Eliminations | Wireless
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(1,263)	(1,239)	(3,746)	(3,707)
Intersegment Eliminations | Cable
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(1,266)	(999)	(3,394)	(2,153)
Intersegment Eliminations | Wireline
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ (6,643)	$ (8,425)	$ (21,591)	$ (24,568)