Preparation of Interim Financial Statements and Other Items - Ownership interest (Details) - Cactus LLC	Sep. 30, 2018	Jul. 16, 2018	Feb. 12, 2018
Other Ownership Interests [Line Items]
Ownership interest (as a percent)	50.30%
Cactus Inc | IPO
Other Ownership Interests [Line Items]
Ownership interest (as a percent)			35.30%
Non-controlling interest owned (as a percentage)			64.70%
Cactus Inc | Follow-on Offering
Other Ownership Interests [Line Items]
Ownership interest (as a percent)		50.30%
Non-controlling interest owned (as a percentage)		49.70%