v3.8.0.1

Related Party Transactions - Management Fees Incurred With Related Parties (Detail) - Property Management Agreement and Asset Management Agreement - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Expenses incurred with related parties	$ 31,646	$ 24,472	$ 21,626
Asset Management Agreement
Related Party Transaction [Line Items]
Expenses incurred with related parties	14,754	10,955	7,042
Property Management Fee
Related Party Transaction [Line Items]
Expenses incurred with related parties	4,988	3,939	2,697
Management Fee Expense
Related Party Transaction [Line Items]
Expenses incurred with related parties	19,742	14,894	9,739
Marketing Fee (Offering Costs)
Related Party Transaction [Line Items]
Expenses incurred with related parties	1,380	1,310	1,796
Acquisition Fee
Related Party Transaction [Line Items]
Expenses incurred with related parties	6,580	5,203	5,501
Leasing Fee
Related Party Transaction [Line Items]
Expenses incurred with related parties	3,339	2,932	4,411
Disposition Fee
Related Party Transaction [Line Items]
Expenses incurred with related parties	$ 605	$ 133	$ 179

X

- Definition

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

+ Details

Name:	us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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

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

X

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=ck0001424182_PropertyManagementAgreementAndAssetManagementAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=ck0001424182_AssetManagementAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=ck0001424182_PropertyManagementFeeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=ck0001424182_ManagementFeeExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=ck0001424182_MarketingFeeOfferingCostsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=ck0001424182_AcquisitionFeeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=ck0001424182_LeasingFeeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=ck0001424182_DispositionFeeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: