Note 10 - Debt (Details Textual) AUD in Millions, $ in Millions		12 Months Ended	14 Months Ended
	Feb. 17, 2017 USD ($)	Dec. 31, 2017 USD ($)	Feb. 16, 2017	Dec. 31, 2017 AUD	Dec. 31, 2016 USD ($)
Interest Coverage Ratio		3
Leverage Ratio		5.85
Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | United States of America, Dollars
Debt Instrument, Basis Spread on Variable Rate	2.25%
Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member] | United States of America, Dollars
Debt Instrument, Basis Spread on Variable Rate	5.50%
Line of Credit [Member] | Base Rate [Member] | Minimum [Member] | United States of America, Dollars
Debt Instrument, Basis Spread on Variable Rate	1.25%
Line of Credit [Member] | Base Rate [Member] | Minimum [Member] | Canada, Dollars
Debt Instrument, Basis Spread on Variable Rate	1.25%
Line of Credit [Member] | Base Rate [Member] | Maximum [Member] | United States of America, Dollars
Debt Instrument, Basis Spread on Variable Rate	4.50%
Line of Credit [Member] | Base Rate [Member] | Maximum [Member] | Canada, Dollars
Debt Instrument, Basis Spread on Variable Rate	4.50%
Line of Credit [Member] | Canadian Dealer Offered Rate (CDOR) [Member] | Minimum [Member] | Canada, Dollars
Debt Instrument, Basis Spread on Variable Rate	2.25%
Line of Credit [Member] | Canadian Dealer Offered Rate (CDOR) [Member] | Maximum [Member] | Canada, Dollars
Debt Instrument, Basis Spread on Variable Rate	5.50%
Line of Credit [Member] | Bank Bill Swap Bid Rate (BBSY) [Member] | Minimum [Member] | Australia, Dollars
Debt Instrument, Basis Spread on Variable Rate	2.25%
Line of Credit [Member] | Bank Bill Swap Bid Rate (BBSY) [Member] | Maximum [Member] | Australia, Dollars
Debt Instrument, Basis Spread on Variable Rate	5.50%
Amended Credit Facility [Member]
Number of Lenders		15		15
Amended Credit Facility [Member] | Minimum [Member]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.51%		0.51%
Lender Commitments, Within Credit Agreement		$ 0.7
Amended Credit Facility [Member] | Maximum [Member]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	1.24%		1.13%
Lender Commitments, Within Credit Agreement		121.7
Amended Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate	2.25%
Amended Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate	5.50%
Amended Credit Facility [Member] | US Term Loan [Member]
Debt Instrument, Face Amount					$ 350.0
Revolving Credit Facility [Member] | Amended Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 275.0				350.0
Line of Credit Facility, Maximum Borrowing Capacity, Increase (Decrease)	(75.0)
Revolving Credit Facility, U.S. Subsidiaries [Member] | Amended Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	40.0				50.0
Letters of Credit Outstanding, Amount		0.8
Revolving Credit Facility, Canadian Subsidiaries [Member] | Amended Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	90.0				100.0
Letters of Credit Outstanding, Amount		0.4
Revolving Credit Facility, The Company [Member] | Amended Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	60.0				100.0
Revolving Credit Facility, Australian Subsidiaries [Member] | Amended Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 85.0				$ 100.0
Letters of Credit Outstanding, Amount		0.6
Bank Guarantee Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity | AUD				AUD 2
Bank Guarantee Outstanding		$ 0.8