Note 15 - Segment Information - Assets by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Long-lived assets	$ 119,686	$ 117,559	$ 109,384
Total assets	79,621	75,057	73,559
United States	108,032	127,316	120,624
UNITED STATES
Long-lived assets	115,451	112,885	104,445
Total assets	77,330	72,562	71,192
United States	91,080	110,785	106,288
CANADA
Long-lived assets	4,235	4,674	4,939
Total assets	2,291	2,495	2,367
United States	$ 16,952	$ 16,531	$ 14,336