CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	8 Months Ended	12 Months Ended
Dec. 31, 2018	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
CASH FLOWS FROM FINANCING ACTIVITIES
Interest capitalized	$ 0	$ 0	$ 431	$ 4,396

Amount of cash paid for interest capitalized, classified as investing activity.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4297-108586

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration