Customer Concentration (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) customer megahertz	Dec. 31, 2017 USD ($)	Dec. 31, 2016	Dec. 31, 1999 renewal megahertz
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Megahertz spectrum range used	1,900			1,900
Number of contract renewals | renewal				2
Length of renewals				10 years
Right or obligation to sell business, percentage of EBV				90.00%
Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Megahertz spectrum range used	2,500,000			2,500,000
Minimum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Megahertz spectrum range used	800			800
Accounts Receivable | Customer Concentration Risk
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Concentration risk, amount | $	$ 43,227	$ 43,405
Concentration risk	79.00%	80.00%
Sales Revenue, Goods, Net | Customer Concentration Risk
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of major customers | customer	1
Concentration risk	68.00%	72.00%	69.00%