Basis of Presentation - Additional Information (Detail) - Joint Venture Transactions	Aug. 31, 2018 Entity
Significant Accounting Policies [Line Items]
Number of joint ventures	3
Spartan
Significant Accounting Policies [Line Items]
Percent of controlling interest by the Company	52.00%
TWB
Significant Accounting Policies [Line Items]
Percent of controlling interest by the Company	55.00%
Worthington Specialty Processing
Significant Accounting Policies [Line Items]
Percent of controlling interest by the Company	51.00%