Summary of Significant Accounting Policies - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Nov. 04, 2019
Finite-Lived Intangible Assets [Line Items]
Advertising expense		$ 2,700,000	$ 3,500,000	$ 2,600,000
Fair value of projected benefit obligations	$ 12,675,000	$ 14,645,000	$ 12,675,000
Stock repurchase amount authorized					$ 80,000,000
Share repurchases (in shares)	200,410
Stock repurchased during period (in dollars per share)	$ 36.08
Common stock, par value (in dollars per share)	$ 0	$ 0	$ 0
Pension Plan
Finite-Lived Intangible Assets [Line Items]
Fair value of projected benefit obligations	$ 6,824,000	$ 7,961,000	$ 6,824,000
Ntelos Holding, Corp | Pension Plan
Finite-Lived Intangible Assets [Line Items]
Fair value of pension plan assets	24,100,000	27,000,000.0	24,100,000
Fair value of projected benefit obligations	$ 30,900,000	$ 34,900,000	$ 30,900,000
Discount rate	3.16%	2.41%	3.16%
Ntelos Pension Plan
Finite-Lived Intangible Assets [Line Items]
Pension benefits, vesting period		5 years
Vesting reductions, threshold age of recipient		65 years
Postretirement Plan
Finite-Lived Intangible Assets [Line Items]
Fair value of projected benefit obligations	$ 3,573,000	$ 3,997,000	$ 3,573,000
Discount rate	3.12%	2.32%	3.12%