Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended										12 Months Ended					12 Months Ended					12 Months Ended				0 Months Ended
	May 31, 2014 Facility JointVentures Country State	May 31, 2013	May 31, 2012	May 31, 2014 Building and Improvements Minimum	May 31, 2014 Building and Improvements Maximum	May 31, 2014 Machinery and Equipment Minimum	May 31, 2014 Machinery and Equipment Maximum	May 31, 2014 Engineered Cabs	May 31, 2013 Engineered Cabs	May 31, 2012 Engineered Cabs	May 31, 2014 Largest Customer Customer	May 31, 2014 Largest Customer Net Sales	May 31, 2014 Ten Largest Customers Net Sales	May 31, 2014 Automotive Market Net Sales	May 31, 2014 Foreign Operations	May 31, 2014 Foreign Operations Net Sales	May 31, 2014 Foreign Operations Pre-tax earnings	May 31, 2014 Collective Bargaining Agreements	May 31, 2014 Joint Venture Transactions Worthington Aritas	May 31, 2014 Joint Venture Transactions Spartan Steel Coating, LLC	May 31, 2014 Joint Venture Transactions TWB	Jul. 31, 2013 Joint Venture Transactions TWB	May 31, 2014 Joint Venture Transactions Worthington Energy Innovations, LLC	May 31, 2014 Joint Venture Transactions Worthington Nitin Cylinders Limited	Jul. 21, 2014 Joint Venture Transactions Severstal Subsequent Event JointVentures	May 31, 2014 WRC Facility	May 31, 2014 Consolidated Entities JointVentures
Significant Accounting Policies [Line Items]
Percent of controlling interest by the company																			75.00%	52.00%	55.00%	55.00%	75.00%	60.00%
Number of assets and interests to be sold																									3
Percentage of additional interest acquired by the company																					10.00%	10.00%
Purchase of additional interest																					$ 17,869,000
Number of production facilities operated	80																									34
Number of States operated	25
Number of Countries operated	10
Number of joint ventures	13																										5
Concentration risk percentage												8.00%	31.00%	36.00%		7.00%	(2.00%)
Percentage of consolidated net assets															15.00%
Percentage of labor force																		4.00%
Number of customers											10
Allowance for doubtful accounts increase (decrease)	(365,000)
Receivables, allowances	3,043,000	3,408,000
Property, plant and equipment, estimated useful life				10 years	40 years	3 years	20 years
Depreciation Expenses	62,344,000	56,002,000	50,644,000
Goodwill	251,093,000	213,858,000	156,681,000					44,933,000	44,933,000	45,230,000
Exceeded carrying value percentage								10.00%
Decrease in long-term growth rate								1.00%
Advertising Expenses	$ 6,788,000	$ 6,179,000	$ 4,788,000