Debt Covenant, Percent Of Note Holders Threshold By Amount Of Principal Outstanding

No definition available.

Name:	bsy_DebtCovenantPercentOfNoteHoldersThresholdByAmountOfPrincipalOutstanding
Namespace Prefix:	bsy_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Convertible, Number of Equity Instruments, Conversion Rate

+ References

No definition available.

+ Details

Name:	bsy_DebtInstrumentConvertibleNumberOfEquityInstrumentsConversionRate
Namespace Prefix:	bsy_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Convertible, Share Price Threshold, Adjustment to Conversion Rate

+ References

No definition available.

+ Details

Name:	bsy_DebtInstrumentConvertibleSharePriceThresholdAdjustmentToConversionRate
Namespace Prefix:	bsy_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Convertible, Threshold Consecutive Business Days

+ References

No definition available.

+ Details

Name:	bsy_DebtInstrumentConvertibleThresholdConsecutiveBusinessDays
Namespace Prefix:	bsy_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Convertible, Threshold Consecutive Trading Days, After Threshold Consecutive Business Days

+ References

No definition available.

+ Details

Name:	bsy_DebtInstrumentConvertibleThresholdConsecutiveTradingDaysAfterThresholdConsecutiveBusinessDays
Namespace Prefix:	bsy_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Trading Days After Maturity Date, Debt Redeemable

+ References

No definition available.

+ Details

Name:	bsy_NumberOfTradingDaysAfterMaturityDateDebtRedeemable
Namespace Prefix:	bsy_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The price per share of the conversion feature embedded in the debt instrument.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031898-161870

+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instrument must exceed threshold percentage for specified number of trading days to trigger conversion feature.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum percentage of common stock price to conversion price of convertible debt instruments to determine eligibility of conversion.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleThresholdTradingDays
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

Name:	us-gaap_DebtInstrumentRedemptionPricePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

+ References

+ Details

Name:	us-gaap_PaymentsOfDebtIssuanceCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for cost incurred directly with the issuance of an equity security.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585

+ Details

Name:	us-gaap_PaymentsOfStockIssuanceCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of cash outflow for payment of an obligation from a lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Name:	us-gaap_RepaymentsOfLinesOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=bsy_TwoThousandTwentySixNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_ConvertibleDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	bsy_DebtInstrumentConvertibleTermsOfConversionAxis=bsy_DebtConversionTermsOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	bsy_DebtInstrumentConvertibleTermsOfConversionAxis=bsy_DebtConversionTermsTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Long‑Term Debt - 2026 Convertible Senior Notes (Details)			9 Months Ended
	Jun. 28, 2021 USD ($)	Jan. 26, 2021 USD ($) share_rate day $ / shares	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Debt Instrument [Line Items]
Payments of debt issuance costs \| $			$ 5,643,000	$ 432,000
2026 Notes: \| Convertible Debt
Debt Instrument [Line Items]
Debt instrument, face amount \| $		$ 690,000,000
Debt instrument, interest rate, stated percentage		0.125%
Payments of debt issuance costs \| $		$ 18,055,000
Payments of expenses associated with initial public offering \| $		25,530,000
Repayment of credit facility \| $	$ 536,062,000	$ 250,500,000
Debt instrument, convertible, threshold percentage of stock price trigger		130.00%
Debt instrument, convertible, threshold trading days		20
Debt instrument, convertible, threshold consecutive trading days		30
Debt instrument, redemption price, percentage		98.00%
Debt instrument, convertible, number of equity instruments, conversion rate \| share_rate		15.5925
Debt instrument, convertible, conversion price (USD per share) \| $ / shares		$ 64.13
Number of trading days after maturity date, debt redeemable		40 days
Effective interest rate		0.658%
2026 Notes: \| Convertible Debt \| Minimum
Debt Instrument [Line Items]
Share price threshold, adjustment to conversion rate (USD per share) \| $ / shares		$ 44.23
2026 Notes: \| Convertible Debt \| Maximum
Debt Instrument [Line Items]
Debt instrument, convertible, number of equity instruments, conversion rate \| share_rate		22.6090
Share price threshold, adjustment to conversion rate (USD per share) \| $ / shares		$ 210.00
Debt covenant, percent of note holders threshold by amount of principal outstanding		25.00%
2026 Notes: \| Convertible Debt \| Debt Conversion Terms One
Debt Instrument [Line Items]
Debt instrument, convertible, threshold trading days		20
Debt instrument, convertible, threshold consecutive trading days		30
2026 Notes: \| Convertible Debt \| Debt Conversion Terms Two
Debt Instrument [Line Items]
Debt instrument, convertible, threshold consecutive business days		5
Debt instrument, convertible, threshold consecutive trading days, after threshold consecutive business days		10