Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
Apr. 30, 2017 USD ($) people state segment merchandise_category store	Apr. 30, 2016 USD ($)	Apr. 30, 2015 USD ($)
Accounting Policies [Abstract]
Number of stores \| store	1,978
Number of states in which entity operates \| state	15
Population of communities (many less than) \| people	5,000
Concentration Risk
Excess of current cost over the stated LIFO Value	$ 65,593	$ 58,432
Goodwill	132,806	128,566
Asset impairment charges	705	1,625	$ 1,785
Recorded asset retirement obligation (net of amortization)	10,421	9,788
Discounted liability of asset retirement obligation	15,899	14,975
Self-insurance reserves	$ 37,984	35,535
Number of operating segments \| segment	1
Number of reportable segments \| segment	1
Number of merchandise categories \| merchandise_category	3
Fuel
Concentration Risk
Excise taxes collected	$ 866,000	$ 818,000	$ 715,000
Fuel \| Retail Sales
Concentration Risk
Concentration risk percentage	59.00%
Grocery & other merchandise \| Retail Sales
Concentration Risk
Concentration risk percentage	28.00%
Prepared food & fountain \| Retail Sales
Concentration Risk
Concentration risk percentage	13.00%

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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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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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