Note 2 - Revenue Recognition - Reconciliation of Contract Assets and Liabilities Associated With Contracts With Customers In Accordance With ASC 606 (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Balance at beginning of period, contract assets	$ 6,898
Contract additions, contract assets	1,902
Amortization, contract assets	(1,806)
Balance at end of period, contract assets	6,994
Balance at beginning of period, contract liabilities	1,150
Contract additions, contract liabilities	1,149
Revenue recognized, contract liabilities	(244)
Balance at end of period, contract liabilities	$ 2,055