XML 125 R110.htm IDEA: XBRL DOCUMENT
v3.25.3

Variable Interest Entities - Additional Information (Detail) - loan | 9 Months Ended | 12 Months Ended
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Sep. 30, 2025 | Dec. 31, 2024
Variable Interest Entity, Primary Beneficiary, Does Not Hold Majority Voting Interest, Disclosures [Abstract] |  |
Number of loans modified | 2 | 2

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- Definition Financing Receivable, Number Of Loans Modified + References No definition available. + Details
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Namespace Prefix: | bxmt_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_VariableInterestEntityPrimaryBeneficiaryDoesNotHoldMajorityVotingInterestDisclosuresAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration