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Supplemental Financial Information (Repair And Maintenance Expense Related To Continuing Operations) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Supplemental Financial Information [Abstract] |  |  |
Repair and maintenance expense | $ 200.4 | $ 303.7 | $ 198.4

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- Definition The aggregate costs of keeping the property in good condition but that do not appreciably prolong the life or increase the value of the property. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 + Details
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Balance Type: | debit
Period Type: | duration

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- Definition Supplemental Financial Information [Abstract] + References No definition available. + Details
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Namespace Prefix: | val_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration