Note 9 - Segment Data (Details) - Financial Information by Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]
Revenues by segment	$ 285,708	$ 259,599	$ 844,848	$ 767,691
Operating income (loss) by segment	30,301	28,756	85,587	79,646
Fluids Systems & Engineering [Member]
Segment Reporting Information [Line Items]
Revenues by segment	233,020	211,457	714,323	632,341
Operating income (loss) by segment	17,140	14,798	57,446	42,273
Mats and Integrated Services [Member]
Segment Reporting Information [Line Items]
Revenues by segment	35,112	35,067	81,108	95,671
Operating income (loss) by segment	15,345	15,992	34,166	43,406
Environmental Services [Member]
Segment Reporting Information [Line Items]
Revenues by segment	17,576	13,075	49,417	39,679
Operating income (loss) by segment	4,656	3,089	13,485	10,178
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating income (loss) by segment	$ (6,840)	$ (5,123)	$ (19,510)	$ (16,211)