Note 2 - Adoption of New Accounting Standard - Cumulative Effect of Adjustments for New Accounting Pronouncements on Consolidated Condensed Balance Sheet (Details) - USD ($) $ in Thousands		Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets:
Prepaid expenses and other		$ 19,876	$ 22,255	$ 19,810
Liabilities:
Accounts payable and accrued liabilities		45,782	40,060	38,100
Stockholders’ equity:
Retained earnings		$ 470,329	$ 449,027	448,542
Accounting Standards Update 2014-09 [Member]
Assets:
Prepaid expenses and other	[1]			2,445
Liabilities:
Accounts payable and accrued liabilities				1,960
Stockholders’ equity:
Retained earnings				$ 485

[1] Contract assets balance at January 1, 2018.