Acquisitions and Divestitures (Acquisitions Narrative) (Details) (USD $)	12 Months Ended				339 Months Ended	12 Months Ended									12 Months Ended
	Mar. 31, 2014 locations		Mar. 31, 2013		Mar. 31, 2014 businesses_acquired locations	Mar. 31, 2014 FY14 Acquisitions [Member] businesses_acquired	Mar. 31, 2014 FY14 Acquisitions [Member] Customer relationships [Member]	Mar. 31, 2014 FY14 Acquisitions [Member] Non-competition agreements [Member]	Mar. 31, 2014 The Encompass Gas Group, Inc. [Member] locations	Mar. 31, 2013 FY13 Acquisitions [Member] businesses_acquired	Mar. 31, 2013 FY13 Acquisitions [Member] Customer relationships [Member]	Mar. 31, 2013 FY13 Acquisitions [Member] Non-competition agreements [Member]	Mar. 31, 2012 FY12 Acquisitions [Member] businesses_acquired	Mar. 31, 2013 FY12 Acquisitions [Member]	Mar. 31, 2012 FY12 Acquisitions [Member] Customer relationships [Member]	Mar. 31, 2012 FY12 Acquisitions [Member] Non-competition agreements [Member]	Mar. 31, 2012 Abco Gases Welding And Industrial Supply Company Inc [Member] locations	Mar. 31, 2012 Pain [Member] locations	Mar. 31, 2012 Nordan Smith Welding [Member] locations
Business Acquisition [Line Items]
Number of businesses acquired					450	11				18			8
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period						$ 82,000,000			$ 55,000,000	$ 95,000,000			$ 106,000,000				$ 35,000,000	$ 33,000,000	$ 31,000,000
Number of locations	1,100				1,100				11								12	20	17
Net Cash Paid For Acquired Businesses And Settlement Of Holdback Liabilities And Contingent Consideration						205,000,000				97,521,000			160,115,000
Business Combination, Integration Related Costs						1,500,000				1,300,000			1,800,000
Net sales from current year acquisitions						33,000,000				30,000,000			58,000,000
Fair value of receivables acquired						8,900,000				9,200,000				12,300,000
Gross contractual amounts of acquired receivables						9,400,000				9,600,000				12,900,000
Goodwill acquired during period	95,410,000	[1]	34,205,000	[1]		93,300,000				35,200,000			48,200,000
Goodwill amount deductible for income tax						89,700,000
Finite-lived Intangible Assets Acquired							$ 55,800,000	$ 4,300,000			$ 30,400,000	$ 11,700,000			$ 34,900,000	$ 6,600,000

[1] Includes acquisitions completed during the respective year and adjustments made to prior year acquisitions.