Note 10 - Credit Agreements (Details Textual) $ in Thousands				1 Months Ended					3 Months Ended			12 Months Ended
		Jul. 01, 2016	May 31, 2013 USD ($)	Oct. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	May 31, 2017	May 31, 2015	Jun. 30, 2018 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2014	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2017 USD ($)	Nov. 30, 2016 USD ($)
Gain Loss on Change in Cash Flows Related to Debt	[1]													$ (2,957)
Secured Leverage Ratio												1.66
Gain (Loss) on Extinguishment of Debt, Total	[2]											$ (1,332)		$ (574)
Long-term Line of Credit, Total
Short-term Debt, Total						20,602						45,583	20,602
ABL Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity					$ 250,000				$ 250,000
Amended ABL Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity					300,000				300,000
Debt Issuance Costs, Net, Total					755				755
Gain (Loss) on Extinguishment of Debt, Total									(34)
Proceeds from Lines of Credit, Total					$ 50,000
Repayments of Lines of Credit				$ 50,000
Long-term Line of Credit, Total												18,459
Line of Credit Facility, Remaining Borrowing Capacity												$ 276,572
Base Rate [Member] | ABL Revolving Credit Facility [Member]
Debt Instrument, Basis Spread on Variable Rate					0.375%			1.00%
Adjusted LIBOR Rate [Member] | ABL Revolving Credit Facility [Member]
Debt Instrument, Basis Spread on Variable Rate					1.375%			2.00%
Term Loan [Member]
Line of Credit Facility, Maximum Borrowing Capacity			$ 1,200,000
Uncommitted Incremental Term Loan Facility			$ 300,000
Net Debt Leverage Ratio Threshold							3			3		3
Gain Loss on Change in Cash Flows Related to Debt										$ 2,957
Debt Issuance Costs, Net, Total						2,346						$ 829	2,346		$ 1,432	$ 4,242
Debt Instrument, Fee Amount						$ 38						$ 118	$ 38		$ 85	$ 315
Secured Leverage Ratio						3.75
Gain (Loss) on Extinguishment of Debt, Total									$ (1,298)
Term Loan [Member] | Net Debt Leverage Ratio Threshold Not Achieved [Member]
Net Debt Leverage Ratio Threshold		3
Term Loan [Member] | Base Rate [Member]
Debt Instrument, Basis Spread on Variable Rate			1.75%		0.75%	1.00%	1.25%
Term Loan [Member] | Base Rate [Member] | Net Debt Leverage Ratio Threshold [Member]
Debt Instrument, Basis Spread on Variable Rate											1.50%
Term Loan [Member] | Adjusted LIBOR Rate [Member]
Debt Instrument, Basis Spread on Variable Rate			2.75%		1.75%	2.00%	2.25%
Term Loan [Member] | Adjusted LIBOR Rate [Member] | Net Debt Leverage Ratio Threshold [Member]
Debt Instrument, Basis Spread on Variable Rate											2.50%
Term Loan [Member] | LIBOR Floor Rate [Member]
Debt Instrument, Basis Spread on Variable Rate			0.75%				0.75%

[1] For the year ended December 31, 2016, represents a non-cash loss relating to the continued 25 basis point increase in borrowing costs as a result of the credit agreement leverage ratio remaining above 3.0 times based on projections at that time. Following the May 2017 Term Loan amendment, which removed the pricing grid based on leverage ratio achieved, gains or losses on changes in contractual interest rate will no longer be recorded in the statements of comprehensive income. Refer to Note 10, "Credit Agreements," to the consolidated financial statements for further information on the gains and losses on changes in the contractual interest rate.

[2] Represents the write-off of original issue discount and capitalized debt issuance costs due to voluntary debt prepayments.