Business Acquisitions - Net sales and net losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Acquisition of Titan
Net sales	$ 833,837	$ 648,004	$ 1,611,981	$ 1,290,161
Operating income	$ 52,095	$ 35,649	85,154	$ 68,336
Titan
Acquisition of Titan
Net sales			214,900
Operating income			$ 7,900

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration