v3.19.3.a.u2

Commitments and Contingencies - Summary of Tenant Improvement Allowances Included in Accounts Payable and Other Liabilities (Detail) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Accounts Payable And Other Liabilities |  |
Loss Contingencies [Line Items] |  |
Tenant improvement allowances | $ 2,706 | $ 2,125

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- Definition Tenant improvement allowances. + References No definition available. + Details
Name: | ck1424182_TenantImprovementAllowances
Namespace Prefix: | ck1424182_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

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- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_AccountsPayableAndAccruedLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |