v3.8.0.1

Notes Receivable - Additional Information (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016
Accounts Notes And Loans Receivable [Line Items] |  |
Notes receivable | $ 6,527 | $ 6,527
7.00% Loan Agreement |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Notes receivable |  | 3,700
Real Estate |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Interest income earned | $ 445 | 77
Real Estate | 7.00% Loan Agreement |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Notes receivable |  | $ 3,700
Interest rate |  | 7.00%
Maturity date |  | 2019-02
Real Estate | 6.35% Loan Agreement |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Notes receivable |  | $ 2,827
Interest rate |  | 6.35%
Maturity date |  | 2019-11

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- Definition Interest income receivable notes receivable. + References No definition available. + Details
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Namespace Prefix: | ck0001424182_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Notes receivable interest rate percentage. + References No definition available. + Details
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Namespace Prefix: | ck0001424182_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Notes receivable maturity date. + References No definition available. + Details
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Namespace Prefix: | ck0001424182_
Data Type: | xbrli:gYearMonthItemType
Balance Type: | na
Period Type: | duration

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

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- Definition Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.3) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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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: |
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Balance Type: |
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- Details
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