Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued Liabilities Detail [Table]
Compensation and employee benefits	$ 22,298	$ 12,681
Oil and gas producing liabilities	9,272	9,335
Unearned income	2,869	6,782
Deferred tax liability	13,860	11,857
Other accrued liabilities	21,091	15,011
Accrued liabilities	$ 69,390	$ 55,666