Note 9 - Segment Data (Details) - Financial Information by Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Segment Reporting Information [Line Items]
Revenues by segment	$ 276,622	$ 245,756	$ 559,140	$ 508,092
Operating income (loss) by segment	26,917	24,755	55,286	50,890
Fluids Systems & Engineering [Member]
Segment Reporting Information [Line Items]
Revenues by segment	233,964	202,388	481,303	420,884
Operating income (loss) by segment	17,684	13,480	40,306	27,475
Mats and Integrated Services [Member]
Segment Reporting Information [Line Items]
Revenues by segment	25,412	30,071	45,996	60,604
Operating income (loss) by segment	10,341	13,075	18,821	27,414
Environmental Services [Member]
Segment Reporting Information [Line Items]
Revenues by segment	17,246	13,297	31,841	26,604
Operating income (loss) by segment	5,321	3,514	8,829	7,089
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating income (loss) by segment	$ (6,429)	$ (5,314)	$ (12,670)	$ (11,088)