Accrued Liabilities (Tables)

3 Months Ended

Mar. 31, 2013

Accrued Liabilities

Schedule of accrued liabilities

	December 31, 2012		March 31, 2013
Salaries and wages	$	4,558	$	5,928
Accrued gas and equipment purchases	10,091		11,699
Derivative liability	112		36
Contingent consideration obligations	70		—
Accrued property and other taxes	4,483		4,524
Accrued professional fees	1,310		1,625
Accrued employee benefits	2,607		3,182
Accrued warranty liability	2,665		2,885
Other	4,898		11,309
	$	30,794	$	41,188