Summary by Business Segment (Financial Information by Segment) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended				26 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2012		Dec. 31, 2011		Mar. 31, 2012
Segment Reporting Information [Line Items]
Gas and rent	$ 772,974		$ 721,455		$ 2,332,093		$ 2,203,272
Hardgoods	434,734		432,296		1,362,481		1,301,862
Total net sales	1,207,708		1,153,751		3,694,574		3,505,134
Cost of products sold (excluding depreciation)	527,452		520,409		1,648,503		1,603,282
Selling, distribution and administrative expenses	462,288		433,050		1,380,720		1,279,933
Restructuring and other special charges (benefits), net	(1,729)		2,431		6,426		18,261
Costs (benefits) related to unsolicited takeover attempt	0		(1,170)		0		(7,870)		60,000
Depreciation	65,804		61,575		194,820		182,224
Amortization	6,614		6,437		19,950		18,841
Operating Income	147,279		131,019		444,155		410,463
Distribution Business Segment [Member]
Segment Reporting Information [Line Items]
Gas and rent	642,884		611,005		1,914,092		1,827,302
Hardgoods	433,218		430,724		1,357,502		1,297,343
Total net sales	1,076,102		1,041,729		3,271,594		3,124,645
Cost of products sold (excluding depreciation)	461,917		467,592		1,441,482		1,413,164
Selling, distribution and administrative expenses	408,704		379,894		1,222,697		1,131,263
Restructuring and other special charges (benefits), net	0		0		0		0
Costs (benefits) related to unsolicited takeover attempt	0		0		0		0
Depreciation	60,372		56,695		178,759		168,026
Amortization	5,384		5,171		16,171		15,075
Operating Income	139,725		132,377		412,485		397,117
All Other Operations Business Segment [Member]
Segment Reporting Information [Line Items]
Gas and rent	138,152		119,409		444,371		404,554
Hardgoods	1,518		1,578		4,984		4,533
Total net sales	139,670		120,987		449,355		409,087
Cost of products sold (excluding depreciation)	73,599		61,782		233,396		218,716
Selling, distribution and administrative expenses	44,866		40,002		130,749		120,258
Restructuring and other special charges (benefits), net	0		0		0		0
Costs (benefits) related to unsolicited takeover attempt	0		0		0		0
Depreciation	5,432		4,880		16,061		14,198
Amortization	1,230		1,266		3,779		3,766
Operating Income	14,543		13,057		65,370		52,149
Eliminations And Other [Member]
Segment Reporting Information [Line Items]
Gas and rent	(8,062)	[1]	(8,959)	[1]	(26,370)	[1]	(28,584)	[1]
Hardgoods	(2)	[1]	(6)	[1]	(5)	[1]	(14)	[1]
Total net sales	(8,064)	[1]	(8,965)	[1]	(26,375)	[1]	(28,598)	[1]
Cost of products sold (excluding depreciation)	(8,064)	[1]	(8,965)	[1]	(26,375)	[1]	(28,598)	[1]
Selling, distribution and administrative expenses	8,718		13,154		27,274		28,412
Restructuring and other special charges (benefits), net	(1,729)		2,431		6,426		18,261
Costs (benefits) related to unsolicited takeover attempt	0		(1,170)		0		(7,870)
Depreciation	0		0		0		0
Amortization	0		0		0		0
Operating Income	$ (6,989)		$ (14,415)		$ (33,700)		$ (38,803)

[1] Amounts in the “Eliminations and Other” column represent the elimination of intercompany sales and associated gross profit on sales from the Company’s All Other Operations business segment to its Distribution business segment.