Recent Accounting Pronouncements - Income Statement (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue									$ 61,025		$ 58,023		$ 49,715
Operating Expenses	$ 12,725	$ 11,567	$ 10,548	$ 11,824	$ 12,665	$ 9,290	$ 9,336	$ 9,528	46,664		40,819		36,509
Income (loss) from operations	1,420	5,650	4,240	(1,331)	4,340	3,550	1,006	353	9,978		9,249		3,426
(Loss) income before income taxes									11,440		9,929		3,713
Benefit from income taxes	(516)	1,339	(11,122)	(357)	(8,971)	310	188	48	(10,653)		(8,425)		(6)
Net income	$ 2,421	$ 4,658	$ 15,743	$ (726)	$ 13,531	$ 3,472	$ 929	$ 422	$ 22,093	[1]	$ 18,354	[1]	$ 3,719	[1]
Basic (in dollars per share)	$ 0.04	$ 0.09	$ 0.29	$ (0.01)	$ 0.25	$ 0.06	$ 0.02	$ 0.03	$ 0.41		$ 0.34		$ 0.07
Diluted (in dollars per share)	$ 0.04	$ 0.08	$ 0.28	$ (0.01)	$ 0.24	$ 0.06	$ 0.02	$ 0.02	$ 0.40		$ 0.33		$ 0.07
Basic (in shares)									53,764		53,701		52,341
Diluted (in shares)									55,338		55,612		55,451
Operating Segments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Expenses									$ 28,512		$ 24,893		$ 20,809
Income (loss) from operations									28,130		25,175		19,126
Operating Segments | Water
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Expenses									10,201		8,883		8,119
Income (loss) from operations									33,100		29,386		23,073
Operating Segments | Oil & Gas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Expenses									18,311		16,010		12,690
Income (loss) from operations									(4,970)		(4,211)		(3,947)
Product
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue	$ 13,983	$ 18,578	$ 17,406	$ 11,058	$ 21,054	$ 13,860	$ 10,864	$ 12,245	61,025		58,023		49,715
Product cost of revenue	3,561	5,022	5,976	3,314	6,660	4,217	3,572	4,612	17,873		19,061		17,849
Product gross profit	10,422	13,556	11,430	7,744	14,394	9,643	7,292	7,633	43,152		38,962		31,866
Product | Operating Segments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue									61,025		58,023		49,715
Product cost of revenue									17,873		19,061		17,849
Product gross profit									43,152		38,962		31,866
Product | Operating Segments | Water
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue									60,512		54,301		47,545
Product cost of revenue									17,211		16,032		16,353
Product gross profit									43,301		38,269		31,192
Product | Operating Segments | Oil & Gas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue									513		3,722		2,170
Product cost of revenue									662		3,029		1,496
Product gross profit									(149)		693		674
License and development revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue	$ 3,723	$ 3,661	$ 3,358	$ 2,749	$ 2,611	$ 3,197	$ 3,050	$ 2,248	13,490		11,106		8,069
License and development revenue | Operating Segments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue									13,490		11,106		8,069
License and development revenue | Operating Segments | Water
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue									0		0		0
License and development revenue | Operating Segments | Oil & Gas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue									13,490		11,106		8,069
Restatement Adjustment | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue									$ 6,000		3,000
Income (loss) from operations											5,973		3,069
(Loss) income before income taxes											5,973		3,069
Benefit from income taxes											(31)		384
Net income											$ 6,004		$ 2,685
Basic (in dollars per share)											$ 0.11		$ 0.05
Diluted (in dollars per share)											$ 0.11		$ 0.05
Basic (in shares)											0		0
Diluted (in shares)											0		0
Restatement Adjustment | Operating Segments | Water | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income (loss) from operations											$ 0		$ 0
Restatement Adjustment | Operating Segments | Oil & Gas | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income (loss) from operations											5,973		3,069
Restatement Adjustment | Product | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											(133)		0
Product cost of revenue											0		0
Product gross profit											(133)		0
Restatement Adjustment | Product | Operating Segments | Water | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											0		0
Product cost of revenue											0		0
Product gross profit											0		0
Restatement Adjustment | Product | Operating Segments | Oil & Gas | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											(133)		0
Product cost of revenue													0
Product gross profit											(133)		0
Restatement Adjustment | License and development revenue | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											6,106		3,069
Restatement Adjustment | License and development revenue | Operating Segments | Oil & Gas | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											6,106		3,069
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income (loss) from operations											3,276		357
(Loss) income before income taxes											3,956		644
Benefit from income taxes											(8,394)		(390)
Net income											$ 12,350		$ 1,034
Basic (in dollars per share)											$ 0.23		$ 0.02
Diluted (in dollars per share)											$ 0.22		$ 0.02
Basic (in shares)											53,701		52,341
Diluted (in shares)											55,612		55,451
As Previously Reported | Operating Segments | Water
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income (loss) from operations											$ 29,386		$ 23,073
As Previously Reported | Operating Segments | Oil & Gas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income (loss) from operations											(10,184)		(7,016)
As Previously Reported | Product
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											58,156		49,715
Product cost of revenue											19,061		17,849
Product gross profit											39,095		31,866
As Previously Reported | Product | Operating Segments | Water
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											54,301		47,545
Product cost of revenue											16,032		16,353
Product gross profit											38,269		31,192
As Previously Reported | Product | Operating Segments | Oil & Gas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											3,855		2,170
Product cost of revenue											3,029		1,496
Product gross profit											826		674
As Previously Reported | License and development revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											5,000		5,000
As Previously Reported | License and development revenue | Operating Segments | Oil & Gas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											$ 5,000		$ 5,000

[1] Due to the full retrospective adoption of ASC 606 as defined in Note 2,”Recent Accounting Pronouncements”, of the Notes to Consolidated Financial Statements in Part II, Item 8, “Financial Statements and Supplemental Data” of this Annual Report on Form 10K, the balances for the years ended 2017 and 2016 were recast.