v3.21.2

Summary of Significant Accounting Policies - Summary of Significant Unobservable Inputs Used to Estimate Fair Value of Earnout Liability (Detail) (Parenthetical) - Measurement Input, Price Volatility [Member] - Fair Value Inputs Level3 [Member]	Feb. 07, 2020
Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Market capitalization rate	6.05%
Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Market capitalization rate	7.09%

X

- Definition

Market capitalization rate.

+ References

No definition available.

+ Details

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Namespace Prefix:	bnl_
Data Type:	dtr-types:percentItemType
Balance Type:	na
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

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

X

- 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:

X

- Details

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

X

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: