Summary of Significant Accounting Policies - ASC 606 Opening Adjustments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	May 31, 2017	Feb. 28, 2019	Feb. 28, 2018	Feb. 28, 2017	Mar. 01, 2018
Assets
Inventories	$ 124,847				$ 110,761				$ 124,847	$ 110,761		$ 118,425
Liabilities and shareholders' equity
Contract liabilities	56,928				22,698				56,928	22,698		29,646
Retained earnings	560,224				526,018				560,224	526,018		526,734
Consolidated Statements of Income
Revenue, Net	202,548	$ 239,516	$ 222,787	$ 262,236	200,660	$ 208,158	$ 196,329	$ 205,283	927,087	810,430	$ 863,538
Cost of goods sold									728,466	650,121	658,206
Gross profit	43,257	$ 49,755	$ 46,904	$ 58,705	38,010	$ 31,117	$ 43,800	$ 47,382	198,621	160,309	205,332
Operating income									76,956	48,248	$ 98,908
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Assets
Inventories	119,627				110,761				119,627	110,761
Liabilities and shareholders' equity
Contract liabilities	53,444				22,698				53,444	22,698
Retained earnings					$ 526,018					$ 526,018
Consolidated Statements of Income
Revenue, Net									923,623
Cost of goods sold									726,022
Gross profit									197,601
Operating income									75,936
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Assets
Inventories	5,220								5,220			7,664
Liabilities and shareholders' equity
Contract liabilities	$ 3,484								3,484			6,948
Retained earnings												$ 716
Consolidated Statements of Income
Revenue, Net									3,464
Cost of goods sold									2,444
Gross profit									1,020
Operating income									$ 1,020