Acquisition - Sprint Territory Expansion (Details) - USD ($)	Feb. 01, 2018	Jun. 30, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
One-time payment for expansion of service area	$ 52,000,000.0
Finite-lived intangible assets	(52,000,000)	$ (332,433,000)	$ (316,504,000)
Maximum
Business Acquisition [Line Items]
One-time payment for expansion of service area, additional payment	$ 5,000,000.0
Affiliate Contract Expansion
Business Acquisition [Line Items]
Estimated useful life, finite lived intangible assets	12 years
Finite-lived intangible assets	$ (45,148,000)	(317,869,000)	(304,193,000)
Prepayment of tangible assets
Business Acquisition [Line Items]
Finite-lived intangible assets	$ (6,497,000)
Off-market leases - favorable
Business Acquisition [Line Items]
Estimated useful life, finite lived intangible assets	16 years 6 months
Finite-lived intangible assets	$ (3,665,000)	$ (14,221,000)	$ (11,881,000)
Off-market leases - unfavorable
Business Acquisition [Line Items]
Estimated useful life, finite lived intangible assets	4 years 2 months 12 days
Finite-lived intangible assets	$ (3,310,000)