Certain issued and outstanding junior subordinated notes pertaining to certain financial covenants.

No definition available.

Name:	bni_DebtInstrumentCovenantDebt
Namespace Prefix:	bni_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Remaining Debt Securities Authorized by the Board

+ References

No definition available.

+ Details

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Namespace Prefix:	bni_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ 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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=bni_SECDebtShelfRegistrationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_JuniorSubordinatedDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bni_FourPointOneFivePercentDebenturesDueDecember152048MemberMemberMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bni_FourPointZeroFivePercentDebenturesDueJune152048MemberMemberMember
Namespace Prefix:
Data Type:	na
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Debt Notes and Debentures (Details) - USD ($) $ in Millions	Sep. 30, 2018	Aug. 02, 2018
SEC Debt Shelf Registration [Member]
Debt Instrument [Line Items]
Remaining Debt Securities Authorized by the Board	$ 250
Junior Subordinated Debt
Debt Instrument [Line Items]
Subordinated notes related to financial covenants	500
Four Point One Five Percent Debentures Due December 15, 2048 [Member] [Member] [Member] [Member] \| Corporate Debt Securities [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 750
Debt Instrument, Interest Rate, Stated Percentage		4.15%
Four Point Zero Five Percent Debentures Due June 15, 2048 [Member] [Member] [Member] \| Corporate Debt Securities [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 750
Debt Instrument, Interest Rate, Stated Percentage	4.05%