Note 7 - Fair Value Measurements (Details Textual) - USD ($) $ in Thousands				12 Months Ended
	Jun. 28, 2019	Jun. 14, 2017	Feb. 02, 2015	Dec. 31, 2019	Dec. 31, 2018	Jan. 15, 2019	Apr. 02, 2015
Deferred Capacity Revenue, Fair Value			$ 41,287
Service Obligation, Carrying Amount				$ 31,113	$ 33,184
Indefeasible Right of Use Assets, Fair Value Disclosure							$ 2,304
Indefeasible Right of Use Obligations, Fair Value Disclosure							$ 4,153
Impairment of Long-Lived Assets to be Disposed of				0	0
Minimum [Member]
Deferred Revenues, Amortization Period			10 years
Maximum [Member]
Deferred Revenues, Amortization Period			30 years
Interest Rate Swap [Member]
Derivative, Final Notional Amount	$ 67,500	$ 90,000
Derivative, Fixed Interest Rate	6.1735%	6.49425%				6.49425%
Derivative, Maturity Date	Jun. 30, 2022
Interest Rate Swap [Member] | London Interbank Offered Rate (LIBOR) [Member]
Derivative, Basis Spread on Variable Rate	4.50%	5.00%				5.00%
Derivative, Maturity Date		Jun. 28, 2019
Senior Credit Facilities and Other Long-Term Obligations [Member]
Debt and Lease Obligation, Total				178,245	$ 172,494
The 2019 Senior Credit Facility [Member]
Debt Instrument Covenants, Minimum Borrowing				$ 90,000
Weighted Average Life of Senior Credit Facility				2 years
Derivative, Final Notional Amount						$ 90,000