XML 96 R65.htm IDEA: XBRL DOCUMENT v3.19.1

Share capital - Narrative (Details) $ in Thousands			2 Months Ended		12 Months Ended
	Oct. 12, 2007 USD ($)	Jun. 29, 2007 shares	Mar. 12, 2019 USD ($)	Mar. 14, 2018 shares	Dec. 31, 2018 USD ($) shares year	Dec. 31, 2018 CAD ($) shares year	Dec. 31, 2017 USD ($) shares year	Dec. 31, 2017 CAD ($) shares year	Dec. 31, 2016 shares
Disclosure of classes of share capital [line items]
Shares issued on exercise of stock options					$ 22,397		$ 25,658
Number of options exercised (in shares) | shares					12,347,000	12,347,000	13,708,000	13,708,000
Common shares issued for cash on exercise of stock options (Note 12)					$ 22,805		$ 26,503
Number of options granted (in shares) | shares					25,380,000	25,380,000	22,968,000	22,968,000
Risk free annual interest rate					2.00%	2.00%	1.30%	1.30%
Dividend yield rate					0.00%	0.00%	0.00%	0.00%
Weighted average share price for share options exercised during period at date of exercise (in Cdn.$per share)						$ 3.55		$ 3.87
Incentive Plan
Disclosure of classes of share capital [line items]
Shares issued on exercise of stock options	$ 4,955
Number of options granted (in shares) | shares		4,955,000
Stock Options
Disclosure of classes of share capital [line items]
Share-based payments expense					$ 18,000		$ 14,000
Term of options granted (in years)					5 years	5 years	5 years	5 years
Award vesting period (in years)					3 years	3 years	3 years	3 years
Fair value of shares from share-based payment transactions					$ 26,000		$ 27,000
Share-based payments expense, capitalized to mining interests					3,000		3,000
Restricted Share Units
Disclosure of classes of share capital [line items]
Share-based payments expense					2,000		4,000
Fair value of shares from share-based payment transactions					$ 4,000		$ 5,000
Number of units granted (in shares) | shares					1,455,000	1,455,000	1,793,000	1,793,000
Deferred Share Unit
Disclosure of classes of share capital [line items]
Share-based payments expense					$ 1,000		$ 1,000
Fair value of shares from share-based payment transactions					$ 1,000		$ 1,000
Measurement period					5 days	5 days
Number of units granted (in shares) | shares					291,000	291,000	225,000	225,000
Bottom of range
Disclosure of classes of share capital [line items]
Exercise price, share options granted (in Cdn.$per share)						$ 2.94		$ 3.27
Expected volatility					56.00%	56.00%	61.00%	61.00%
Top of range
Disclosure of classes of share capital [line items]
Exercise price, share options granted (in Cdn.$per share)						$ 3.44		$ 4.05
Expected option life (in years) | year					3	3	3	3
Expected volatility							62.00%	62.00%
Vesting 1 year from grant | Restricted Share Units
Disclosure of classes of share capital [line items]
Award vesting percent					33.33%	33.33%
Vesting 2 years from grant | Restricted Share Units
Disclosure of classes of share capital [line items]
Award vesting period (in years)					2 years	2 years
Award vesting percent					33.33%	33.33%
Vesting 3 years from grant | Restricted Share Units
Disclosure of classes of share capital [line items]
Award vesting period (in years)					3 years	3 years
Award vesting percent					33.33%	33.33%
Ordinary shares
Disclosure of classes of share capital [line items]
Number of shares outstanding (in shares) | shares					994,621,917
Number of shares held in trust under the Company's Incentive Plan (in shares) | shares					1,705,000
Preference shares
Disclosure of classes of share capital [line items]
Number of shares outstanding (in shares) | shares					0
Share capital
Disclosure of classes of share capital [line items]
Number of shares outstanding (in shares) | shares					994,622,000		980,933,000		964,892,000
Shares issued on exercise of stock options					$ 22,397		$ 25,658
Number of options exercised (in shares) | shares					12,173,000	12,173,000	13,343,000	13,343,000
Major ordinary share transactions
Disclosure of classes of share capital [line items]
Common shares issued for cash on exercise of stock options (Note 12)			$ 20,000
Major ordinary share transactions | Ordinary shares | Stock Options
Disclosure of classes of share capital [line items]
Number of options exercised (in shares) | shares				10,000,000

X

- Definition

Expense From Share-Based Payment Transactions With Employees, Capitalized To Mining Interests

+ References

No definition available.

+ Details

Name:	btg_ExpenseFromShareBasedPaymentTransactionsWithEmployeesCapitalizedToMiningInterests
Namespace Prefix:	btg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Fair Value Of Shares From Share-Based Payment Transactions

+ References

No definition available.

+ Details

Name:	btg_FairValueOfSharesFromShareBasedPaymentTransactions
Namespace Prefix:	btg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Share-Based Compensation Arrangement By Share-Based Payment Award, Award Vesting Period2

+ References

No definition available.

+ Details

Name:	btg_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod2
Namespace Prefix:	btg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Share Capital, Share Based Compensation, Measurement Period

+ References

No definition available.

+ Details

Name:	btg_ShareCapitalShareBasedCompensationMeasurementPeriod
Namespace Prefix:	btg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Share-based Compensation Arrangement By Share-based Payment Award, Expiration Period1

+ References

No definition available.

+ Details

Name:	btg_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod1
Namespace Prefix:	btg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Share-based Compensation By Share-based Payment Award, Other Equity Instruments Portion Vesting, Percent

+ References

No definition available.

+ Details

Name:	btg_SharebasedCompensationBySharebasedPaymentAwardOtherEquityInstrumentsPortionVestingPercent
Namespace Prefix:	btg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The expected volatility of the share price used to calculate the fair value of the share options granted. Expected volatility is a measure of the amount by which a price is expected to fluctuate during a period. The measure of volatility used in option pricing models is the annualised standard deviation of the continuously compounded rates of return on the share over a period of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 47
-Subparagraph a
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_47_a_i&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_DescriptionOfExpectedVolatilityShareOptionsGranted
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The option life of share options granted.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 47
-Subparagraph a
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_47_a_i&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_DescriptionOfOptionLifeShareOptionsGranted
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The implied yield currently available on zero-coupon government issues of the country in whose currency the exercise price for share options granted is expressed, with a remaining term equal to the expected term of the option being valued (based on the option's remaining contractual life and taking into account the effects of expected early exercise). [Refer: Government [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 47
-Subparagraph a
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_47_a_i&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_DescriptionOfRiskFreeInterestRateShareOptionsGranted
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

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

+ References

No definition available.

+ Details

Name:	ifrs-full_DisclosureOfClassesOfShareCapitalLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The exercise price of share options granted.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 47
-Subparagraph a
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_47_a_i&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_ExercisePriceShareOptionsGranted
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The percentage of an expected dividend used to calculate the fair value of share options granted.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 47
-Subparagraph a
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_47_a_i&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_ExpectedDividendAsPercentageShareOptionsGranted
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The amount of expense from share-based payment transactions with employees.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 112
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_112_c&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_ExpenseFromSharebasedPaymentTransactionsWithEmployees
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

The increase (decrease) in equity resulting from the exercise of options.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 106
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_106_d&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_IncreaseDecreaseThroughExerciseOfOptions
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

The number of other equity instruments (ie other than share options) granted in a share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 47
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_47_b&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_45&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_NumberOfInstrumentsOtherEquityInstrumentsGranted
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The number of share options exercised in a share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 45
-Subparagraph b
-Clause iv
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_45_b_iv&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_NumberOfShareOptionsExercisedInSharebasedPaymentArrangement
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The number of share options granted in a share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 45
-Subparagraph b
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_45_b_ii&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_NumberOfShareOptionsGrantedInSharebasedPaymentArrangement
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The number of shares that have been authorised and issued, reduced by treasury shares held. [Refer: Treasury shares]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 79
-Subparagraph a
-Clause iv
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_79_a_iv&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_NumberOfSharesOutstanding
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The cash inflow from the exercise of options.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2017-01-01
-Paragraph 17
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2017-03-01&anchor=para_17&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_ProceedsFromExerciseOfOptions
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

The number of shares in the entity held by the entity or by its subsidiaries or associates. [Refer: Associates [member]; Subsidiaries [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 79
-Subparagraph a
-Clause vi
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_79_a_vi&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_SharesInEntityHeldByEntityOrByItsSubsidiariesOrAssociates
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The weighted average share price at the date of exercise for share options that are exercised in a share-based payment arrangement. [Refer: Share-based payment arrangements [member]; Weighted average [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 45
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_45_c&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_WeightedAverageExercisePriceOfShareOptionsInSharebasedPaymentArrangementExercisedDuringPeriodAtDateOfExercise
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=btg_IncentivePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=btg_StockOptionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=btg_RestrictedShareUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=btg_DeferredShareUnitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	btg_Vesting1Axis=btg_Tranche1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	btg_Vesting1Axis=btg_Tranche2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	btg_Vesting1Axis=btg_Tranche3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_ClassesOfShareCapitalAxis=ifrs-full_OrdinarySharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_ClassesOfShareCapitalAxis=ifrs-full_PreferenceSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_ComponentsOfEquityAxis=ifrs-full_IssuedCapitalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_NonadjustingEventsAfterReportingPeriodAxis=ifrs-full_MajorOrdinaryShareTransactionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: