Restatement of Previously Issued Financial Statements - Balance Sheets (Details) - USD ($) $ in Thousands	May 31, 2017	Feb. 28, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Inventories - net	$ 101,026
Costs and estimated earnings in excess of billings on uncompleted contracts	57,198	$ 50,262
Total current assets	325,486	297,052
Total assets	1,004,740	978,354
Other accrued liabilities	25,375	24,042
Customer deposits	1,711	1,459
Billings in excess of costs and estimated earnings on uncompleted contracts	22,539	20,617
Total current liabilities	126,730	136,770
Deferred income tax liabilities	53,823	53,648
Total liabilities	466,031	445,218
Retained earnings	506,166	498,527
Total shareholders’ equity	538,709	533,136
Total liabilities and shareholders' equity	1,004,740	$ 978,354
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Inventories - net	131,187
Costs and estimated earnings in excess of billings on uncompleted contracts	27,295
Total current assets	325,744
Total assets	1,004,998
Other accrued liabilities	22,067
Customer deposits	23,629
Billings in excess of costs and estimated earnings on uncompleted contracts	7,898
Total current liabilities	130,699
Deferred income tax liabilities	52,431
Total liabilities	468,608
Retained earnings	503,847
Total shareholders’ equity	536,390
Total liabilities and shareholders' equity	1,004,998
Correction
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Inventories - net	(30,161)
Costs and estimated earnings in excess of billings on uncompleted contracts	29,903
Total current assets	(258)
Total assets	(258)
Other accrued liabilities	3,308
Customer deposits	(21,918)
Billings in excess of costs and estimated earnings on uncompleted contracts	14,641
Total current liabilities	(3,969)
Deferred income tax liabilities	1,392
Total liabilities	(2,577)
Retained earnings	2,319
Total shareholders’ equity	2,319
Total liabilities and shareholders' equity	$ (258)