Schedule of Consideration Transferred and Fair Value Assigned to Assets Acquired And Liabilities Assumed (Detail) - Entity [Domain] - USD ($) $ in Thousands	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Estimated Fair Value of Assets Acquired and Liabilities Assumed:
Goodwill	$ 238,999	$ 251,093	$ 213,858
Rome Strip Steel
Consideration Transferred:
Cash consideration	55,312
Purchase price	54,495
Plus: estimated working capital deficit	817
Estimated Fair Value of Assets Acquired and Liabilities Assumed:
Cash	10
Accounts receivable	6,333
Inventories	17,063
Prepaid expenses	41
Intangible assets	5,500
Property, plant and equipment	22,775
Total identifiable assets	51,722
Accounts payable	(3,091)
Other accrued items	(410)
Other liabilities	(313)
Net assets	47,908
Goodwill	6,587
DHybrid Systems Llc
Consideration Transferred:
Cash consideration	11,939
Fair value of contingent consideration	3,979
Purchase price	15,918
Estimated Fair Value of Assets Acquired and Liabilities Assumed:
Cash	1,132
Accounts receivable	1,482
Inventories	2,732
Prepaid expenses	38
Intangible assets	3,788
Property, plant and equipment	406
Total identifiable assets	9,578
Accounts payable	(1,867)
Accrued liabilities	(533)
Long-term debt	(5,000)
Net assets	2,178
Goodwill	17,822
Cash consideration	20,000
Noncontrolling interest	(4,082)
Total consideration	15,918
MEF
Consideration Transferred:
Cash consideration	38,441
Estimated Fair Value of Assets Acquired and Liabilities Assumed:
Accounts receivable	3,329
Inventories	3,550
Intangible assets	13,600
Property, plant and equipment	166
Total identifiable assets	20,645
Accounts payable	(555)
Other accrued items	(92)
Deferred revenue	(4,808)
Net assets	15,190
Goodwill	23,251
Cash consideration	38,441
JRE
Consideration Transferred:
Cash consideration	1,571
Estimated Fair Value of Assets Acquired and Liabilities Assumed:
Cash	253
Accounts receivable	509
Inventories	2,793
Prepaid expenses	40
Property, plant and equipment	250
Total identifiable assets	3,845
Accounts payable	(514)
Other accrued items	(2,160)
Net assets	1,171
Goodwill	400
Cash consideration	1,571
Steffes
Consideration Transferred:
Cash consideration	27,962
Estimated Fair Value of Assets Acquired and Liabilities Assumed:
Inventories	2,316
Intangible assets	10,290	10,290
Property, plant and equipment	2,638
Total identifiable assets	15,244
Goodwill	12,718
Cash consideration	27,962
Worthington Aritas
Consideration Transferred:
Fair value of contingent consideration	404
Purchase price	35,325
Estimated Fair Value of Assets Acquired and Liabilities Assumed:
Cash		1,037
Accounts receivable		3,242
Inventories		10,678
Prepaid expenses		1,317
Intangible assets	16,800	16,800
Other noncurrent assets		1,099
Property, plant and equipment		5,467
Total identifiable assets		39,640
Accounts payable		(5,587)
Short-term borrowings		(251)
Accrued liabilities		(6,902)
Deferred taxes		(2,787)
Net assets		24,113
Goodwill		22,987
Cash consideration		47,100
Noncontrolling interest		(11,775)
Total consideration		35,325
Worthington Aritas | Preliminary Valuation
Estimated Fair Value of Assets Acquired and Liabilities Assumed:
Cash		1,037
Accounts receivable		3,326
Inventories		10,678
Prepaid expenses		1,317
Intangible assets		16,800
Other noncurrent assets		1,099
Property, plant and equipment		5,467
Total identifiable assets		39,724
Accounts payable		(5,587)
Short-term borrowings		(251)
Accrued liabilities		(2,756)
Other liabilities		(4,954)
Deferred taxes		(2,787)
Net assets		23,389
Goodwill		23,586
Cash consideration		46,975
Noncontrolling interest		(11,744)
Total consideration		35,231
Worthington Aritas | Measurement Period Adjustments
Estimated Fair Value of Assets Acquired and Liabilities Assumed:
Accounts receivable		(84)
Total identifiable assets		(84)
Accrued liabilities		(4,146)
Other liabilities		4,954
Net assets		724
Goodwill		(599)
Cash consideration		125
Noncontrolling interest		(31)
Total consideration		$ 94
TWB
Consideration Transferred:
Cash consideration	17,869
Fair value of previously held equity interest in TWB	72,369
Total consideration	90,238
Estimated Fair Value of Assets Acquired and Liabilities Assumed:
Cash	70,826
Accounts receivable	52,012
Inventories	20,403
Prepaid expenses	4,027
Intangible assets	22,028
Other noncurrent assets	103
Property, plant and equipment	52,390
Total identifiable assets	221,789
Accounts payable	(50,642)
Accrued liabilities	(6,431)
Deferred taxes	(2,109)
Cash consideration	162,607
Noncontrolling interest	(72,369)
Total consideration	$ 90,238