v3.21.2

Non-Controlling Interests - Schedule of OP Units Exchanged for Shares of Common Stock (Detail) - USD ($) shares in Thousands, $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Mar. 31, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Noncontrolling Interest [Line Items] |  |  |  |  |
Value of shares/units exchanged |  | $ 0 |  | $ 46,220 |
Common Stock |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |
OP Units exchanged for shares of common stock | 1,723 |  | 0 | 2,888 | 0
Value of shares/units exchanged |  | 0 |  |  |
Additional Paid-in Capital |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |
Value of shares/units exchanged | $ 27,755 | $ 606 | $ 0 | $ 46,220 | $ 0

X
- Definition Number of op units exchanged. + References No definition available. + Details
Name: | bnl_NumberOfOpUnitsExchanged
Namespace Prefix: | bnl_
Data Type: | xbrli:sharesItemType
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
Name: | us-gaap_MinorityInterestLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Value of stock issued during the period upon the conversion of units. An example of a convertible unit is an umbrella partnership real estate investment trust unit (UPREIT unit). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29-31) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=123467817&loc=d3e21463-112644 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770 + Details
Name: | us-gaap_StockIssuedDuringPeriodValueConversionOfUnits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AdditionalPaidInCapitalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |