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Short-term and Other Investments (Short-term) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($) item	Dec. 31, 2015 USD ($)
Short-term investments
Amortized cost | $	$ 8,955	$ 11,990
Minimum days for maturity | item	90

X

- Definition

Amortized cost of short-term investments in debt and equity securities and other forms of securities that provide ownership interests classified as available-for-sale.

+ References

No definition available.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesShortTermInvestmentsAmortizedCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- References

No definition available.

+ Details

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

X

- Definition

Represents the minimum number of days for maturity for short-term investments of the entity.

+ References

No definition available.

+ Details

Name:	vgz_ShortTermInvestmentsMinimumMaturityDays
Namespace Prefix:	vgz_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration