Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
Apr. 30, 2018 USD ($) people state segment store merchandise_category	Apr. 30, 2017 USD ($)	Apr. 30, 2016 USD ($)
Accounting Policies [Abstract]
Number of stores \| store	2,073
Number of states in which entity operates \| state	16
Population of communities (many less than) \| people	5,000
Concentration Risk
Excess of current cost over the stated LIFO Value	$ 73,494	$ 65,593
Goodwill	140,258	132,806
Asset impairment charges	507	705	$ 1,625
Recorded asset retirement obligation (net of amortization)	11,280	10,421
Discounted liability of asset retirement obligation	17,087	15,899
Self insurance reserve	$ 39,777	37,984
Number of operating segments \| segment	1
Number of reportable segments \| segment	1
Number of merchandise categories \| merchandise_category	3
Insurance accruals, current	$ 20,029	18,816
Insurance accruals, net of current portion	19,748	19,168
Fuel
Concentration Risk
Excise taxes collected	$ 919,000	$ 866,000	$ 818,000
Fuel \| Retail Sales
Concentration Risk
Concentration risk percentage	61.00%
Grocery & other merchandise \| Retail Sales
Concentration Risk
Concentration risk percentage	27.00%
Prepared food & fountain \| Retail Sales
Concentration Risk
Concentration risk percentage	12.00%

The recorded asset for asset retirement obligations is recorded in other assets,net of amortization.

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Population of Communities

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The excess of replacement or current cost over the stated LIFO (last in first out) inventory value when the LIFO inventory method is utilized.

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The excise taxes collected by a public utility and reported in revenues if the amount of excise taxes is equal to 1 percent or more of such total.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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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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