Acquisitions - Narrative (Details) customer in Thousands, $ in Thousands			3 Months Ended				9 Months Ended
	Apr. 06, 2017 customer	May 06, 2016 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Business Acquisition [Line Items]
Integration and acquisition expenses			$ 1,706		$ 15,272		$ 9,873	$ 35,801
Ntelos Holding, Corp
Business Acquisition [Line Items]
Aggregate purchase price		$ 667,800
Measurement period adjustment, amortization expense				$ 100
Measurement period adjustment, depreciation expense						$ 4,600
Integration and acquisition expenses			2,900		20,200		15,400	43,900
Term extend for affiliate relationship agreement		5 years
Limit of waived feed under affiliate agreement		$ 251,800
Period for additional waiver of management fee under affiliate agreement		6 months
Minimum | Ntelos Holding, Corp
Business Acquisition [Line Items]
Before amendment right or obligation to sell business		80.00%
Maximum | Ntelos Holding, Corp
Business Acquisition [Line Items]
After amendment right or obligation to sell business		90.00%
Management fee charge by Sprint		$ 4,200
Additional waiver of management fee under affiliate agreement		$ 5,000
Sprint and Affiliates | Sprint PCS Management Agreement, Former Retail, Post and Prepaid Subscribers, Sprint-branded Affiliate Customers
Business Acquisition [Line Items]
Number of customers | customer	25
Other | Operating Segments
Business Acquisition [Line Items]
Integration and acquisition expenses			$ 15		$ 800		$ 266	$ 15,900