Investments in Unconsolidated Affiliates - Financial Results of Four Largest Unconsolidated Affiliates (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		May 31, 2021	Feb. 28, 2021	Nov. 30, 2020	Aug. 31, 2020	May 31, 2020	Feb. 29, 2020	Nov. 30, 2019	Aug. 31, 2019	May 31, 2021	May 31, 2020	May 31, 2019
Investments In And Advances To Affiliates [Line Items]
Net sales		$ 978,319	$ 759,109	$ 731,092	$ 702,909	$ 611,627	$ 763,996	$ 827,637	$ 855,859	$ 3,171,429	$ 3,059,119	$ 3,759,556
Gross margin (loss)		226,148	164,098	135,474	113,358	89,890	115,545	120,611	117,291	639,078	443,337	479,955
Operating income (loss)										310,600	223,521	221,549
Depreciation and amortization										34,988	30,519	26,483
Interest expense										12,284	13,992	13,395
Income tax expense (benefit)										11,960	3,453	7,877
Net earnings		$ 118,542	$ 72,683	$ (68,512)	$ 618,738	$ 11,089	$ 18,888	$ 56,922	$ (2,455)	741,450	84,444	163,273
Equity Method Investment, Nonconsolidated Investee, Other
Investments In And Advances To Affiliates [Line Items]
Net sales										1,918,477	1,819,996	1,857,811
Gross margin (loss)										438,558	376,930	341,278
Net earnings										293,186	259,450	209,232
WAVE
Investments In And Advances To Affiliates [Line Items]
Operating income (loss)										165,381	166,404	166,969
Depreciation and amortization										4,073	4,032	3,634
Interest expense										8,909	11,061	10,547
Income tax expense (benefit)										200	216	219
WAVE | Equity Method Investment, Nonconsolidated Investee, Other
Investments In And Advances To Affiliates [Line Items]
Net sales										371,814	368,820	379,103
Gross margin (loss)										215,692	208,040	205,909
Net earnings	[1]									156,869	202,451	162,849
ClarkDietrich
Investments In And Advances To Affiliates [Line Items]
Operating income (loss)										94,888	66,952	33,384
Depreciation and amortization										11,917	11,869	11,600
Interest expense										101	378	912
ClarkDietrich | Equity Method Investment, Nonconsolidated Investee, Other
Investments In And Advances To Affiliates [Line Items]
Net sales										893,371	855,994	892,758
Gross margin (loss)										158,074	131,619	93,947
Net earnings										98,313	68,899	34,560
Serviacero Worthington
Investments In And Advances To Affiliates [Line Items]
Operating income (loss)										43,075	7,513	25,636
Depreciation and amortization										4,305	4,324	4,319
Interest expense										42	87	493
Income tax expense (benefit)										11,341	3,267	7,629
Serviacero Worthington | Equity Method Investment, Nonconsolidated Investee, Other
Investments In And Advances To Affiliates [Line Items]
Net sales										311,543	273,276	351,671
Gross margin (loss)										51,253	15,739	34,494
Net earnings										31,865	2,573	16,155
ArtiFlex
Investments In And Advances To Affiliates [Line Items]
Operating income (loss)										9,628	6,248	5,524
Depreciation and amortization										5,728	5,605	6,055
Interest expense										528	801	1,443
Income tax expense (benefit)										149	(15)	29
ArtiFlex | Equity Method Investment, Nonconsolidated Investee, Other
Investments In And Advances To Affiliates [Line Items]
Net sales										144,834	175,428	201,526
Gross margin (loss)										20,596	14,212	12,928
Net earnings										8,950	5,461	4,051
Other [Member]
Investments In And Advances To Affiliates [Line Items]
Operating income (loss)										(2,372)	(23,596)	(9,964)
Depreciation and amortization										8,965	4,689	875
Interest expense										2,704	1,665
Income tax expense (benefit)										270	(15)
Other [Member] | Equity Method Investment, Nonconsolidated Investee, Other
Investments In And Advances To Affiliates [Line Items]
Net sales										196,915	146,478	32,753
Gross margin (loss)										(7,057)	7,320	(6,000)
Net earnings										$ (2,811)	$ (19,934)	$ (8,383)

[1] On September 30, 2019, WAVE completed the sale of its international operations to Knauf Ceilings and Holding GmbH (“Knauf”), as part of the broader transaction between Knauf and Armstrong World Industries, Inc., our partner in the WAVE joint venture.  The net earnings in this table include net income attributable to discontinued operations of  $49,770,000 and $6,830,000 in fiscal 2020 and fiscal 2019, respectively.  All other amounts presented in the table above exclude the activity of the discontinued operations of WAVE.