v3.20.2

Commitments and Contingencies - Additional Information (Detail) $ in Thousands | 6 Months Ended
--- | ---
Jun. 30, 2020 USD ($)
Loss Contingencies [Line Items] |
Potential liability due to taxable sales of applicable properties | $ 22,300
Minimum | Office Lease |
Loss Contingencies [Line Items] |
Non-cancellable operating leases, expiration year | 2020
Minimum | Ground Lease |
Loss Contingencies [Line Items] |
Non-cancellable operating leases term | 2034
Maximum | Office Lease |
Loss Contingencies [Line Items] |
Non-cancellable operating leases, expiration year | 2023
Maximum | Ground Lease |
Loss Contingencies [Line Items] |
Non-cancellable operating leases term | 2066

X
- Definition Non cancellable operating leases expiration year. + References No definition available. + Details
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Namespace Prefix: | ck1424182_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Non-cancellable operating leases term. + References No definition available. + Details
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Namespace Prefix: | ck1424182_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Potential liability due to taxable sales of applicable properties. + References No definition available. + Details
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Namespace Prefix: | ck1424182_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- 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
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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |