Preparation of Interim Financial Statements and Other Items - Deferred tax components (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Components of deferred tax assets and liabilties
Investments in Cactus Wellhead	$ 70,307
Foreign loss carryforwards	382	$ 489
Foreign credits	105
Deferred tax assets	70,794	489
Valuation allowance	(487)	(489)
Deferred tax asset, net	70,307
Foreign withholding taxes	712	416
Deferred tax liability, net	$ 712	$ 416