Note 8 - Debt (Details Textual) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
	Apr. 17, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 15, 2019
Proceeds from Lines of Credit, Total				$ 20,933	$ 72,291	$ 6,000
Repayments of Lines of Credit				76,000	18,500	6,000
Interest Expense, Debt, Total				1,200	1,000	200
Credit Facility [Member]
Debt Agreement, Maximum Borrowing Capacity	$ 165,000
Long-term Debt, Total			$ 76,000	0	54,500
Proceeds from Debt Agreement			20,900
Debt Issuance Costs, Net, Total				1,200
Repayments of Lines of Credit		$ 76,000
Amortization of Debt Issuance Costs				800
Interest Payable, Current				$ 100	300	$ 100
Credit Facility [Member] | Base Rate [Member] | Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate	0.50%
Credit Facility [Member] | Base Rate [Member] | Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate	1.00%
Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate	1.50%
Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate	2.00%
Credit Facility [Member] | Revolving Credit Facility [Member]
Long-term Debt, Total					14,000
Line of Credit Facility, Maximum Borrowing Capacity	$ 35,000						$ 35,000
Debt Issuance Costs, Net, Total		800
Proceeds from Lines of Credit, Total			7,000
Credit Facility [Member] | Draw Term Loan [Member]
Long-term Debt, Total	$ 130,000				40,500		$ 55,000
Proceeds from Issuance of Long-term Debt, Total			13,900
Debt Issuance Costs, Net, Total		$ 600	$ 100		$ 600