Name:	blkb_AnnualDividendperShareApproved
Namespace Prefix:	blkb_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

Base Salary Requirement for One-Time Bonus

No definition available.

Name:	blkb_BaseSalaryRequirementforOneTimeBonus
Namespace Prefix:	blkb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Grant date fair value of award under share-based payment arrangement. Excludes share and unit options.

No definition available.

Name:	blkb_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsGrantDateFairValue
Namespace Prefix:	blkb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

No definition available.

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

Percentage employer matches of the employee's percentage contribution matched.

No definition available.

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

Payments of cash to employees, including wages and salaries, during the current period.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 17
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3367-108585

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

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

Name:	us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis=blkb_COVID19Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: