Revenue from Contracts with Customers - Revenue by Category (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 154,030	$ 153,258	$ 305,762	$ 307,138
Wireless
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	111,038	112,899	220,197	227,128
Cable
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	31,014	28,978	61,694	57,423
Wireline
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	11,978	$ 11,381	23,871	$ 22,587
Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	163,505		325,321
Operating Segments | Wireless service
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	93,219		182,978
Operating Segments | Wireless equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	15,819		33,193
Operating Segments | Business, residential and enterprise
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	39,979		79,801
Operating Segments | Tower and other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	14,488		29,349
Operating Segments | Wireless
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	112,282		222,680
Operating Segments | Wireless | Wireless service
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	93,219		182,978
Operating Segments | Wireless | Wireless equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	15,819		33,193
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	3,244		6,509
Operating Segments | Cable
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	32,111		63,822
Operating Segments | Cable | Wireless service
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Cable | Wireless equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Cable | Business, residential and enterprise
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	29,466		58,597
Operating Segments | Cable | Tower and other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2,645		5,225
Operating Segments | Wireline
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	19,112		38,819
Operating Segments | Wireline | Wireless service
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Wireline | Wireless equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Wireline | Business, residential and enterprise
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	10,513		21,204
Operating Segments | Wireline | Tower and other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	8,599		17,615
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(9,475)		(19,559)
Intersegment Eliminations | Wireless
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(1,244)		(2,483)
Intersegment Eliminations | Cable
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(1,097)		(2,128)
Intersegment Eliminations | Wireline
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ (7,134)		$ (14,948)