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Equity Method Investment in ARO - Schedule of Related Parties (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
ARO
Schedule of Equity Method Investments [Line Items]
Lease revenue	$ 14.2	$ 16.6

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

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- Definition

Lease Revenue From Related Party

+ References

No definition available.

+ Details

Name:	val_LeaseRevenueFromRelatedParty
Namespace Prefix:	val_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=val_AROMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: