Derivative Instruments (Schedule Of Estimated Amount Of Net Gains Associated With Derivatives) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net unrealized gains to be reclassified to contract drilling expense	$ 3.4
Net realized gains to be reclassified to depreciation expense	0.8
Net gains to be reclassified to earnings	$ 4.2

Net Unrealized Gains (Losses) To Be Reclassified To Contract Drilling Expense

No definition available.

Name:	val_NetUnrealizedGainsLossesToBeReclassifiedToContractDrillingExpense
Namespace Prefix:	val_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant