Note 9 - Long-term Debt and Credit Facility (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Mar. 12, 2018	Oct. 31, 2015
Line of Credit Facility, Fees		$ 3,100
Line of Credit Facility, Up Front Lending Fee		1,400
Line of Credit Facility, Third Party Arrangement Fees		1,700
Long-term Debt, Total	$ 278,520	314,219
Repayments of Lines of Credit	7,000	7,000
Long-term Debt, Fair Value	286,800	307,700
Derivative, Fixed Interest Rate			2.937%
Bayou [Member]
Repayment of (Proceeds From) Divestiture of Businesses		35,000
A 2015 Interest Rate Swap [Member]
Derivative Asset, Notional Amount				$ 262,500
Derivative, Fixed Interest Rate				1.46%
A 2018 Interest Rate Swap [Member]
Derivative Asset, Notional Amount			$ 170,600
Derivative, Fixed Interest Rate			2.937%
Derivative, Amount of Hedged Item			$ 170,600
Term Loan [Member]
Long-term Debt, Total	253,800
A 2015 Credit Facility [Member]
Debt Instrument, Face Amount				$ 650,000
Line of Credit Facility, Maximum Borrowing Capacity				350,000
Line Of Credit Facility, Unamortized Loan Costs		2,400
Interest Expense, Debt, Total		600
Long-term Line of Credit, Total	24,000	31,000
Other Loans Payable, Total	800	1,000
Letters of Credit Outstanding, Amount	$ 26,100
Proceeds from Lines of Credit, Total		$ 28,000
Derivative, Amount of Hedged Item				262,500
Credit Facility Maximum Consolidated Leverage Ratio	3.25
Credit Facility Actual Consolidated Leverage Ratio	2.88
Line of Credit Facility, Remaining Borrowing Capacity	$ 37,500
Credit Facility Minimum Consolidated Fixed Charge Ratio	1.25
Credit Facility Actual Consolidated Fixed Charge Ratio	1.38
A 2015 Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | A 2015 Interest Rate Swap [Member]
Debt Instrument, Interest Rate, Effective Percentage	4.09%
A 2015 Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate		1.25%
A 2015 Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate		2.25%
A 2015 Credit Facility [Member] | Term Loan [Member]
Debt Instrument, Face Amount		$ 308,400
Debt Instrument, Interest Rate, Effective Percentage	3.83%
Long-term Debt, Total		$ 282,200
A 2015 Credit Facility [Member] | Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity				$ 225,000
A 2015 Credit Facility [Member] | Insurance Carries Collateral [Member]
Letters of Credit Outstanding, Amount	$ 12,200
A 2015 Credit Facility [Member] | Working Performance Obligation [Member]
Letters of Credit Outstanding, Amount	$ 13,900