Revenue from Contracts with Customers - Revenue by Category (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ (161,484)	$ (158,731)	$ (156,501)	$ (154,138)	$ (151,617)	$ (152,382)	$ (153,867)	$ (154,125)	$ (630,854)	$ (611,991)	$ (535,288)
Wireless
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(457,639)	(450,129)	(384,133)
Cable
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(124,197)	(115,917)	(106,997)
Wireline
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(49,018)	(45,945)	(44,158)
Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(668,700)
Operating Segments | Wireless service
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(380,818)
Operating Segments | Equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(68,398)
Operating Segments | Business, residential and enterprise
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(160,281)
Operating Segments | Tower and other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(59,203)
Operating Segments | Wireless
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(462,655)	(455,078)	(388,753)
Operating Segments | Wireless | Wireless service
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(380,818)
Operating Segments | Wireless | Equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(67,510)
Operating Segments | Wireless | Business, residential and enterprise
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									0
Operating Segments | Wireless | Tower and other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(14,327)
Operating Segments | Cable
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(128,903)	(119,162)	(108,734)
Operating Segments | Cable | Wireless service
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									0
Operating Segments | Cable | Equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(695)
Operating Segments | Cable | Business, residential and enterprise
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(117,836)
Operating Segments | Cable | Tower and other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(10,372)
Operating Segments | Wireline
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(77,142)	(79,253)	(74,974)
Operating Segments | Wireline | Wireless service
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									0
Operating Segments | Wireline | Equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(193)
Operating Segments | Wireline | Business, residential and enterprise
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(42,445)
Operating Segments | Wireline | Tower and other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(34,504)
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									37,846	41,502	37,173
Intersegment Eliminations | Wireless
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(5,016)	(4,949)	(4,620)
Intersegment Eliminations | Cable
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									(4,706)	(3,245)	(1,737)
Intersegment Eliminations | Wireline
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									$ (28,124)	$ (33,308)	$ (30,816)