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Impact of Adoption of Standards Related to Revenue Recognition (Details) - USD ($)
Nov. 30, 2018
Jun. 01, 2018
May 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]      
Inventory $ 12,081,725   $ 11,317,775
Costs and estimated earnings in excess of billings 5,953,406   6,356,963
Billings in excess of costs and estimated earnings 793,578   2,043,002
Other accrued expenses 1,818,422   1,412,502
Retained earnings 28,080,428   26,959,080
Calculated under Revenue Guidance in Effect before Topic 606 [Member]      
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]      
Inventory 12,081,725 $ 12,418,891 11,317,775
Costs and estimated earnings in excess of billings 5,953,406 6,030,454 6,356,963
Billings in excess of costs and estimated earnings   2,017,897 2,043,002
Other accrued expenses 1,818,422 2,207,215 1,412,502
Retained earnings $ 28,080,428 26,964,079 $ 26,959,080
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]      
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]      
Inventory   1,101,116  
Costs and estimated earnings in excess of billings   (326,509)  
Billings in excess of costs and estimated earnings   (25,105)  
Other accrued expenses   794,713  
Retained earnings   $ 4,999