Summary by Business Segment (Financial Information by Segment) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended												12 Months Ended						26 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2014		Mar. 31, 2013		Mar. 31, 2012		Mar. 31, 2012
Segment Reporting Information [Line Items]
Total net sales	$ 1,267,830	$ 1,242,846	$ 1,281,970	$ 1,279,891	$ 1,262,923		$ 1,207,708		$ 1,229,610		$ 1,257,256		$ 5,072,537		$ 4,957,497		$ 4,746,283
Cost of products sold (excluding depreciation))													2,247,574		2,235,567		2,175,430
Selling, distribution and administrative expenses													1,889,123		1,828,524		1,727,769
Restructuring and other special charges, net					1,663		(1,729)		2,443		5,712		0		8,089		24,448
Costs (benefits) related to unsolicited takeover attempt													0		0		(7,870)		60,000
Depreciation													275,461		261,622		245,076
Amortization													29,845		27,278		25,209
Operating Income	150,232	154,919	168,769	156,614	152,261	[1]	147,279	[1]	145,186	[1]	151,690	[1]	630,534		596,417		556,221
Assets	5,793,314				5,618,225								5,793,314		5,618,225		5,320,585		5,320,585
Capital expenditures													354,587		325,465		356,514
Distribution Business Segment [Member]
Segment Reporting Information [Line Items]
Total net sales													4,558,790		4,398,105		4,234,869
Cost of products sold (excluding depreciation))													1,996,065		1,958,573		1,918,108
Selling, distribution and administrative expenses													1,705,408		1,620,651		1,528,215
Restructuring and other special charges, net															0		0
Costs (benefits) related to unsolicited takeover attempt																	0
Depreciation													252,329		240,167		225,723
Amortization													25,512		22,297		20,139
Operating Income													579,476		556,417		542,684
Assets	5,222,781				5,047,042								5,222,781		5,047,042		4,816,034		4,816,034
Capital expenditures													317,066		300,431		333,271
All Other Operations Business Segment [Member]
Segment Reporting Information [Line Items]
Total net sales													544,154		593,598		549,213
Cost of products sold (excluding depreciation))													281,916		311,200		295,121
Selling, distribution and administrative expenses													176,289		174,643		162,205
Restructuring and other special charges, net															0		0
Costs (benefits) related to unsolicited takeover attempt																	0
Depreciation													23,132		21,455		19,353
Amortization													4,333		4,981		5,070
Operating Income													58,484		81,319		67,464
Assets	570,533				571,183								570,533		571,183		504,551		504,551
Capital expenditures													37,521		25,034		23,243
Gas and rent [Member]
Segment Reporting Information [Line Items]
Total net sales													3,226,822		3,131,022		2,967,559
Gas and rent [Member] | Distribution Business Segment [Member]
Segment Reporting Information [Line Items]
Total net sales													2,717,272		2,577,901		2,462,232
Gas and rent [Member] | All Other Operations Business Segment [Member]
Segment Reporting Information [Line Items]
Total net sales													539,954		587,322		543,111
Hardgoods [Member]
Segment Reporting Information [Line Items]
Total net sales													1,845,715		1,826,475		1,778,724
Hardgoods [Member] | Distribution Business Segment [Member]
Segment Reporting Information [Line Items]
Total net sales													1,841,518		1,820,204		1,772,637
Hardgoods [Member] | All Other Operations Business Segment [Member]
Segment Reporting Information [Line Items]
Total net sales													4,200		6,276		6,102
Eliminations And Other [Member]
Segment Reporting Information [Line Items]
Total net sales													(30,407)	[2]	(34,206)	[2]	(37,799)	[2]
Cost of products sold (excluding depreciation))													(30,407)	[2]	(34,206)	[2]	(37,799)	[2]
Selling, distribution and administrative expenses													7,426		33,230		37,349
Restructuring and other special charges, net															8,089		24,448
Costs (benefits) related to unsolicited takeover attempt																	(7,870)
Depreciation													0		0		0
Amortization													0		0		0
Operating Income													(7,426)		(41,319)		(53,927)
Assets	0				0								0		0		0		0
Capital expenditures													0		0		0
Eliminations And Other [Member] | Gas and rent [Member]
Segment Reporting Information [Line Items]
Total net sales													(30,404)		(34,201)		(37,784)
Eliminations And Other [Member] | Hardgoods [Member]
Segment Reporting Information [Line Items]
Total net sales													$ (3)		$ (5)		$ (15)

[1] Operating income includes the following items:

[2] 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.