Assets Measured at Fair Value on Non-recurring Basis (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2012
Fair Value [Line Items]
Asset measured at fair value on nonrecurring basis	$ 6,934
Impairment of long-lived assets	1,570
Long-lived assets held for sale
Fair Value [Line Items]
Asset measured at fair value on nonrecurring basis	6,934	[1]
Pressure Cylinders
Fair Value [Line Items]
Impairment of long-lived assets	1,570
Pressure Cylinders | Long-lived assets held for sale
Fair Value [Line Items]
Asset measured at fair value on nonrecurring basis	$ 6,934

[1] During the first quarter of fiscal 2013, certain assets within our Pressure Cylinders operating segment met the applicable criteria for classification as assets held for sale. Accordingly, this asset group is presented separately in our consolidated balance sheet as assets held for sale. The net book value of the asset group was determined to be in excess of fair value, and, as a result, the asset group was written down to its fair value less cost to sell, or $6,934,000, resulting in an impairment charge of $1,570,000. This impairment charge 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.