Commitments and Contingencies - Other (Details) $ in Millions, $ in Millions	3 Months Ended	12 Months Ended
Jan. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)	Jan. 31, 2019 AUD ($)
Commitments and Contingencies Disclosure [Abstract]
Decrease in precious scrap metals		$ 8.5
Compulsory acquisition offer			$ 48.0
Proceeds from advances, percentage of total compensation (percent)	90.00%
Proceeds from advances	$ 31.1

The increase (decrease) during the reporting period in the value of raw materials, packaging materials and supplies held in inventory.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

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