v3.21.2

Sale of Real Estate - Schedule of Sale of Real Estate (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) Property	Sep. 30, 2020 USD ($) Property	Sep. 30, 2021 USD ($) Property	Sep. 30, 2020 USD ($) Property
Real Estate [Line Items]
Number of properties disposed | Property	6	5	25	18
Aggregate sale price	$ 26,567	$ 9,816	$ 71,905	$ 57,539
Aggregate carrying value	(24,244)	(8,327)	58,817	(45,085)
Gain on sale of real estate	1,220	1,060	9,791	9,725
Real Estate
Real Estate [Line Items]
Additional sales expenses	(1,103)	(429)	(3,297)	(2,729)
Gain on sale of real estate	$ 1,220	$ 1,060	$ 9,791	$ 9,725

X

- Definition

Carrying value of real estate, sold.

+ References

No definition available.

+ Details

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Namespace Prefix:	bnl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Number of rental property disposed.

+ References

No definition available.

+ Details

Name:	bnl_NumberOfRentalPropertyDisposed
Namespace Prefix:	bnl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The difference between the carrying value and the sale price of real estate or properties that were intended to be sold or held for capital appreciation or rental income. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2941-110230

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=123351718&loc=d3e2443-110228

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Cash received for the sale of real estate that is not part of an investing activity during the current period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3179-108585

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

X

- Definition

Expenses recognized in the period that are directly related to the selling and distribution of products or services.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.4)
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

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Balance Type:	debit
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X

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: