Summary by Business Segment (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information [Line Items]
Number of business segments	2
Revenues derived from foreign countries	$ 85	$ 84	$ 83
Long-lived assets attributable to foreign operations	$ 168	$ 157	$ 146
Percentage of total sales of largest customer	0.50%
Distribution Business Segment [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	1
Number of operating segments	20
Sales revenue, gas and rent percentage	60.00%	59.00%	58.00%
Sales revenue, hardgoods percentage	40.00%	41.00%	42.00%
Revenues from Distribution business segment, percentage	90.00%	90.00%	90.00%
All Other Operations Business Segment [Member]
Segment Reporting Information [Line Items]
Number of operating segments	6
Maximum [Member]
Segment Reporting Information [Line Items]
Long-lived assets in foreign countries as percentage of consolidated total long-lived assets	4.00%

Long-Lived Assets in Foreign Countries as Percentage of Consolidated Total Long-Lived Assets

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- Definition

Number Of Business Segments

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- Definition

Percentage of total sales of largest customer.

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- Definition

revenue net, percentage

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- Definition

Sales Revenue, Gas and Rent Percentage

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- Definition

Sales Revenue, Hardgoods Percentage

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- Definition

Long-lived assets other than financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 280

-SubTopic 10

-Section 50

-Paragraph 41

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9038-108599

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- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

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