Assets Measured at Fair Value on Non-recurring Basis (Parenthetical) (Detail) (USD $)	12 Months Ended									3 Months Ended		3 Months Ended			3 Months Ended		3 Months Ended					1 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended
	May 31, 2012	May 31, 2011	May 31, 2010	May 31, 2012 Long-lived assets held and used		May 31, 2011 Long-lived assets held and used		May 31, 2011 Long-lived assets held for sale		May 31, 2012 Global Group	May 31, 2012 Global Group Long-lived assets held and used	May 31, 2011 Metal Framing	May 31, 2011 Metal Framing Long-lived assets held and used	May 31, 2011 Metal Framing Long-lived assets held for sale	May 31, 2011 Commercial Stairs	May 31, 2011 Commercial Stairs Long-lived assets held and used	May 31, 2011 Steel Packaging	May 31, 2011 Steel Packaging Long-lived assets held and used	May 31, 2011 Metal Framing Facility Long-lived assets held for sale	Mar. 02, 2011 MISA Metals, Inc	May 31, 2011 MISA Metals, Inc Long-lived assets held for sale	Mar. 02, 2011 Joint Venture Transactions ClarkDietrich	May 31, 2011 Joint Venture Transactions ClarkDietrich	May 09, 2011 Joint Venture Transactions ArtiFlex	May 31, 2011 Joint Venture Transactions ArtiFlex	May 31, 2011 Joint Venture Transactions Long-lived assets held and used ArtiFlex
Fair Value [Line Items]
Asset measured at fair value on nonrecurring basis	$ 225,000	$ 123,743,000		$ 225,000	[1]	$ 27,408,000	[2]	$ 9,681,000	[3]		$ 225,000		$ 21,125,000	$ 3,797,000		$ 400,000		$ 500,000	$ 3,797,000							$ 9,180,000
Impairment of long-lived assets	355,000	4,386,000	35,409,000							355,000		18,293,000			2,473,000		1,913,000					18,293,000	18,293,000	6,414,000	6,414,000
Percent of interest by unconsolidated affiliates																						25.00%		50.00%
Interest recorded at acquisition-date fair value																						58,250,000		28,404,000
Business acquisition, asset acquired																				$ 88,777,000	$ 5,884,000

[1] During the fourth quarter of fiscal 2012, due largely to changes in the intended use of certain long-lived assets within our Global Group operating segment, we determined indicators of impairment were present. Recoverability of the identified asset group was tested using future cash flow projections based on management's long range estimates of market conditions. The sum of these undiscounted future cash flows was less than the net book value of the asset group. The net book value was also determined to be in excess of fair value and, accordingly, the asset group was written down to its fair value of $225,000, resulting in an impairment charge of $355,000. This impairment loss was recorded within impairment of long-lived assets in our consolidated statement of earnings. Fair value was determined based on market prices for similar assets.

[2] During the fourth quarter of fiscal 2011, due largely to changes in the intended use of certain long-lived within our Metal Framing operating segment, we determined indicators of impairment were present. Recoverability of the identified assets was tested using future cash flow projections based on management's estimate of market conditions. The sum of these undiscounted future cash flows was less than the net book value of the asset group. The net book value was also determined to be in excess of fair value and, accordingly, the asset group was written down to its fair value of $21,125,000, resulting in an impairment charge of $18,293,000. This impairment charge was recognized within the joint venture transactions line in our consolidated statement of earnings to correspond with amounts previously recognized in connection with the formation of ClarkDietrich. Fair value was determined based on market prices for similar assets. Certain assets retained subsequently met the criteria for classification as assets held for sale. In accordance with the applicable accounting guidance, the net assets of these facilities were presented separately as assets held for sale in our consolidated balance sheet as of May 31, 2011. As the related assets had previously been written down to their fair value of $3,797,000, no additional impairment charges were recognized. The results of these facilities continued to be reported within operating income as they did not qualify for classification as a discontinued operation. During the fourth quarter of fiscal 2011, due largely to changes in the intended use of certain long-lived assets within our former Automotive Body Panels operating segment, we determined indicators of impairment were present. Recoverability of the identified asset group was tested using future cash flow projections based on management's long range estimates of market conditions. The sum of these undiscounted future cash flows was less than the net book value of the asset group. The net book value was also determined to be in excess of fair value and, accordingly, the asset group was written down to its fair value of $9,180,000, resulting in an impairment charge of $6,414,000. This impairment charge was recognized within the joint venture transactions line in our consolidated statement of earnings to correspond with amounts previously recognized in connection with the formation of ArtiFlex. Fair value was determined based on market prices for similar assets. During the fourth quarter of fiscal 2011, due largely to changes in the intended use of certain long-lived assets within our Commercial Stairs business unit, we determined indicators of impairment were present. Recoverability of the identified asset group was tested using future cash flow projections based on management's long range estimates of market conditions. The sum of these undiscounted future cash flows was less than the net book value of the asset group. The net book value was also determined to be in excess of fair value and, accordingly, the asset group was written down to its fair value of $400,000, resulting in an impairment charge of $2,473,000. This impairment loss was recorded within impairment of long-lived assets in our consolidated statement of earnings. Fair value was determined based on market prices for similar assets. During the fourth quarter of fiscal 2011, due largely to changes in the intended use of certain long-lived assets within our Steel Packaging operating segment, we determined indicators of impairment were present. Recoverability of the identified asset group was tested using future cash flow projections based on management's long range estimates of market conditions. The sum of these undiscounted future cash flows was less than the net book value of the asset group. The net book value was also determined to be in excess of fair value and, accordingly, the asset group was written down to its fair value of $500,000, resulting in an impairment charge of $1,913,000. This impairment loss was recorded within impairment of long-lived assets in our consolidated statement of earnings. Fair value was determined based on market prices for similar assets.

[3] During the fourth quarter of fiscal 2011, we committed to plans to sell certain steel processing assets acquired in connection with the MMI acquisition, thereby meeting the criteria for classification as assets held for sale. In accordance with the applicable accounting guidance, these assets were presented separately as assets held for sale in our consolidated balance sheet as of May 31, 2011. As the acquired assets were recorded at their acquisition-date fair value of $5,884,000, no impairment charges were recognized. Fair value was determined based on market prices for similar assets. The results of these facilities continued to be reported within operating income as they did not qualify for classification as a discontinued operation. During the fourth quarter of fiscal 2011, the assets of certain of the retained metal framing facilities met the criteria for classification as assets held for sale. In accordance with the applicable accounting guidance, the net assets of these facilities are presented separately as assets held for sale in our consolidated balance sheet as of May 31, 2011. As the related assets had previously been written down to their fair value of $3,797,000, no additional impairment charges were recognized. Fair value was determined based on market prices for similar assets.