Asset Impairment Charges	12 Months Ended
Mar. 31, 2013
Asset Impairment Charges [Abstract]
Asset Impairment Charges	ASSET IMPAIRMENT CHARGES As a result of an impairment analysis performed on the long-lived assets associated with a reporting unit in the Company’s All Other Operations business segment, the Company recorded a charge of $1.7 million related to certain of the intangible assets associated with this business during the three months ended June 30, 2012 (see Note 7). The charge was reflected in the “Restructuring and other special charges, net” line item of the Company’s Consolidated Statement of Earnings and was not allocated to the Company’s business segments (see Note 21). No other impairment charges were recorded for the fiscal year ended March 31, 2013. In August 2011, the Company received 24 months notice that a supplier’s hydrogen plant, which generates carbon dioxide as a by-product that serves as the feedstock for the Company’s co-located liquid carbon dioxide plant, will cease operations in calendar year 2013. The Company expects the hydrogen plant to continue to supply the feedstock for its liquid carbon dioxide plant during the intervening period. Additionally, in March 2012, the Company re-evaluated its plan for the operation of one of its smaller and less efficient air separation units over the long-term. In accordance with guidance for the impairment of long-lived assets, the Company separately evaluated the fixed assets at the liquid carbon dioxide plant and air separation unit for recovery. Using the undiscounted expected future cash flows for each asset group, the Company determined that the undiscounted expected future cash flows of the fixed assets at both locations were not sufficient to support the respective carrying values of the assets. In order to determine whether an impairment existed for either group of fixed assets, the fair values of the respective asset groups were estimated using internally developed discounted cash flow models. Factors such as expected future revenues and margins, the likelihood of asset redeployment and the length of the remaining operating terms were considered in determining the future cash flows of the fixed assets. As a result of the impairment analysis performed on the assets at the liquid carbon dioxide production facility, Airgas recorded a charge of $2.5 million in September 2011 to adjust the carrying value of the plant assets to the Company’s estimated fair value. The Company recorded a similar charge of $1.8 million in March 2012 related to the air separation unit. The impairment charges are reflected in the “Restructuring and other special charges, net” line item of the Company’s Consolidated Statements of Earnings and were not allocated to the Company’s business segments (see Note 21).

ASSET IMPAIRMENT CHARGES

As a result of an impairment analysis performed on the long-lived assets associated with a reporting unit in the Company’s All Other Operations business segment, the Company recorded a charge of $1.7 million related to certain of the intangible assets associated with this business during the three months ended June 30, 2012 (see Note 7). The charge was reflected in the “Restructuring and other special charges, net” line item of the Company’s Consolidated Statement of Earnings and was not allocated to the Company’s business segments (see Note 21). No other impairment charges were recorded for the fiscal year ended March 31, 2013.

In August 2011, the Company received 24 months notice that a supplier’s hydrogen plant, which generates carbon dioxide as a by-product that serves as the feedstock for the Company’s co-located liquid carbon dioxide plant, will cease operations in calendar year 2013. The Company expects the hydrogen plant to continue to supply the feedstock for its liquid carbon dioxide plant during the intervening period. Additionally, in March 2012, the Company re-evaluated its plan for the operation of one of its smaller and less efficient air separation units over the long-term.

In accordance with guidance for the impairment of long-lived assets, the Company separately evaluated the fixed assets at the liquid carbon dioxide plant and air separation unit for recovery. Using the undiscounted expected future cash flows for each asset group, the Company determined that the undiscounted expected future cash flows of the fixed assets at both locations were not sufficient to support the respective carrying values of the assets. In order to determine whether an impairment existed for either group of fixed assets, the fair values of the respective asset groups were estimated using internally developed discounted cash flow models. Factors such as expected future revenues and margins, the likelihood of asset redeployment and the length of the remaining operating terms were considered in determining the future cash flows of the fixed assets.

As a result of the impairment analysis performed on the assets at the liquid carbon dioxide production facility, Airgas recorded a charge of $2.5 million in September 2011 to adjust the carrying value of the plant assets to the Company’s estimated fair value. The Company recorded a similar charge of $1.8 million in March 2012 related to the air separation unit. The impairment charges are reflected in the “Restructuring and other special charges, net” line item of the Company’s Consolidated Statements of Earnings and were not allocated to the Company’s business segments (see Note 21).