v3.8.0.1

Schedule III - Real Estate Assets and Accumulated Depreciation (Parenthetical) (Detail) $ in Thousands | Dec. 31, 2017 USD ($)
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Real Estate And Accumulated Depreciation Disclosure [Abstract] |
Aggregate cost of real estate owned | $ 2,500,000

X
- Definition Cost of real estate gross. + References No definition available. + Details
Name: | ck0001424182_CostOfRealEstateGross
Namespace Prefix: | ck0001424182_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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