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

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=119993939&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

+ 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

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

- Definition

Amount, before accumulated amortization, of debt issuance costs related to line of credit arrangements. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section S45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=68176171&loc=SL68176184-208336

+ Details

Name:	us-gaap_DebtIssuanceCostsLineOfCreditArrangementsGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 4: 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))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Definition

Amount of long-term debt and lease obligation, classified as noncurrent.

+ References

+ Details

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

- Definition

Amount of long-term debt and lease obligation, classified as current.

+ References

+ Details

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

- Definition

Amount of long-term debt and lease obligation, including portion classified as current.

+ References

No definition available.

+ Details

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

- Definition

Amount of long-term debt classified as other.

+ 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))
-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 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

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

Debt and Financing Arrangements Long-Term Debt (Details)	Sep. 30, 2020 USD ($)	Sep. 30, 2020 EUR (€)	Sep. 30, 2020 JPY (¥)	Sep. 30, 2019 USD ($)
Debt Instrument [Line Items]
Other Long-term Debt	$ 8,000,000			$ 3,000,000
Long-term Debt and Capital Lease Obligations, Including Current Maturities	7,822,000,000			7,240,000,000
Less: current portion	262,000,000			501,000,000
Debt Issuance Costs, Line of Credit Arrangements, Gross	34,000,000			31,000,000
Net long-term debt	$ 7,526,000,000			6,708,000,000
Four Point Six Two Five Percent Due in Two Thousand Twenty Three [Member] \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.625%	4.625%	4.625%
Debt instrument, face amount	$ 25,000,000
Long-term Debt	$ 26,000,000			26,000,000
Four Point Six Two Five Percent Due in Two Thousand Twenty Three [Member] \| Tyco International Finance S.A. (TIFSA) [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.625%	4.625%	4.625%
Debt instrument, face amount	$ 7,000,000
Long-term Debt	$ 7,000,000			7,000,000
5.0 % Due in 2020 \| Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.00%	5.00%	5.00%
Debt instrument, face amount	$ 47,000,000
Long-term Debt	$ 0			47,000,000
5.0 % Due in 2020 \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.00%	5.00%	5.00%
Debt instrument, face amount	$ 453,000,000
Long-term Debt	$ 0			453,000,000
Zero Point Zero Percent Due Two Thousand Twenty-One [Member] \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.00%	0.00%	0.00%
Debt instrument, face amount \| €		€ 750,000,000
Long-term Debt	$ 0			818,000,000
4.25% Due in 2021 \| Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.25%	4.25%	4.25%
Debt instrument, face amount	$ 53,000,000
Long-term Debt	$ 53,000,000			53,000,000
4.25% Due in 2021 \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.25%	4.25%	4.25%
Debt instrument, face amount	$ 204,000,000
Long-term Debt	$ 204,000,000			204,000,000
3.75 % Due in 2022 \| Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.75%	3.75%	3.75%
Debt instrument, face amount	$ 22,000,000
Long-term Debt	$ 22,000,000			22,000,000
3.75 % Due in 2022 \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.75%	3.75%	3.75%
Debt instrument, face amount	$ 171,000,000
Long-term Debt	$ 171,000,000			171,000,000
One Point Zero Percent Due Two Thousand Twenty Three \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.00%	1.00%	1.00%
Debt instrument, face amount \| €		€ 888,000,000
Long-term Debt	$ 1,039,000,000			967,000,000
Three Point Six Two Five Percent Due Two Thousand Twenty Four [Member] \| Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.625%	3.625%	3.625%
Debt instrument, face amount	$ 31,000,000
Long-term Debt	$ 31,000,000			31,000,000
Three Point Six Two Five Percent Due Two Thousand Twenty Four [Member] \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.625%	3.625%	3.625%
Debt instrument, face amount	$ 453,000,000
Long-term Debt	$ 453,000,000			453,000,000
One Point Three Seven Five Percent Due in Two Thousand Twenty Five [Member] \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.375%	1.375%	1.375%
Debt instrument, face amount \| €		€ 423,000,000
Long-term Debt	$ 503,000,000			471,000,000
One Point Three Seven Five Percent Due in Two Thousand Twenty Five [Member] \| Tyco International Finance S.A. (TIFSA) [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.375%	1.375%	1.375%
Debt instrument, face amount \| €		€ 54,000,000
Long-term Debt	$ 64,000,000			60,000,000
Three Point Ninety Percent Due in Two Thousand Twenty Six [Member] \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.90%	3.90%	3.90%
Debt instrument, face amount	$ 487,000,000
Long-term Debt	$ 516,000,000			521,000,000
Three Point Ninety Percent Due in Two Thousand Twenty Six [Member] \| Tyco International Finance S.A. (TIFSA) [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.90%	3.90%	3.90%
Debt instrument, face amount	$ 51,000,000
Long-term Debt	$ 51,000,000			51,000,000
Six Point Zero Percent Due Two Thousand Thirty Six [Member] \| Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.00%	6.00%	6.00%
Debt instrument, face amount	$ 8,000,000
Long-term Debt	$ 8,000,000			8,000,000
Six Point Zero Percent Due Two Thousand Thirty Six [Member] \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.00%	6.00%	6.00%
Debt instrument, face amount	$ 342,000,000
Long-term Debt	$ 339,000,000			339,000,000
Five Point Seven Percent Due Two Thousand Forty One \| Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.70%	5.70%	5.70%
Debt instrument, face amount	$ 30,000,000
Long-term Debt	$ 30,000,000			30,000,000
Five Point Seven Percent Due Two Thousand Forty One \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.70%	5.70%	5.70%
Debt instrument, face amount	$ 190,000,000
Long-term Debt	$ 189,000,000			189,000,000
Five Point Two Five Percent Due Two Thousand Forty Two \| Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.25%	5.25%	5.25%
Debt instrument, face amount	$ 6,000,000
Long-term Debt	$ 6,000,000			6,000,000
Five Point Two Five Percent Due Two Thousand Forty Two \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.25%	5.25%	5.25%
Debt instrument, face amount	$ 155,000,000
Long-term Debt	$ 155,000,000			155,000,000
Four Point Six Two Five Percent Due Two Thousand Forty Four \| Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.625%	4.625%	4.625%
Debt instrument, face amount	$ 6,000,000
Long-term Debt	$ 6,000,000			6,000,000
Four Point Six Two Five Percent Due Two Thousand Forty Four \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.625%	4.625%	4.625%
Debt instrument, face amount	$ 444,000,000
Long-term Debt	$ 441,000,000			441,000,000
Five Point One Two Five Percent Due in Two Thousand Forty Five [Member] \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.125%	5.125%	5.125%
Debt instrument, face amount	$ 477,000,000
Long-term Debt	$ 564,000,000			567,000,000
Five Point One Two Five Percent Due in Two Thousand Forty Five [Member] \| Tyco International Finance S.A. (TIFSA) [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.125%	5.125%	5.125%
Debt instrument, face amount	$ 23,000,000
Long-term Debt	$ 22,000,000			22,000,000
Six Point Nine Five Percent Due Two Thousand Forty Six \| Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.95%	6.95%	6.95%
Debt instrument, face amount	$ 4,000,000
Long-term Debt	$ 4,000,000			4,000,000
Six Point Nine Five Percent Due Two Thousand Forty Six \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.95%	6.95%	6.95%
Debt instrument, face amount	$ 32,000,000
Long-term Debt	$ 32,000,000			32,000,000
Four point five percent maturing in fiscal 2047 [Member] \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.50%	4.50%	4.50%
Debt instrument, face amount	$ 500,000,000
Long-term Debt	$ 496,000,000			496,000,000
Four Point Nine Five Percent Due Two Thousand Sixty Four [Member] \| Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.95%	4.95%	4.95%
Debt instrument, face amount	$ 15,000,000
Long-term Debt	$ 15,000,000			15,000,000
Four Point Nine Five Percent Due Two Thousand Sixty Four [Member] \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.95%	4.95%	4.95%
Debt instrument, face amount	$ 341,000,000
Long-term Debt	$ 340,000,000			340,000,000
LIBOR JPY Plus Zero Point Four Two Percent Due in Two Thousand Twenty Two [Member] \| Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.40%	0.40%	0.40%
Debt instrument, face amount \| ¥			¥ 25,000,000,000
Long-term Debt	$ 237,000,000			232,000,000
Zero Point Three Seven Five Percent Due Two Thousand Twenty Seven \| Johnson Controls International plc (JCI) and Tyco Fire & Security Finance S.C.A. (TFSCA)
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.375%	0.375%	0.375%
Debt instrument, face amount \| €		€ 500,000,000
Long-term Debt	$ 583,000,000			0
One Point Seven Five Percent Due Two Thousand Thirty \| Johnson Controls International plc (JCI) and Tyco Fire & Security Finance S.C.A. (TFSCA)
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.75%	1.75%	1.75%
Debt instrument, face amount	$ 625,000,000
Long-term Debt	$ 623,000,000			0
One Point Zero Percent Due Two Thousand Thirty Two \| Johnson Controls International plc (JCI) and Tyco Fire & Security Finance S.C.A. (TFSCA)
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.00%	1.00%	1.00%
Debt instrument, face amount \| €		€ 500,000,000
Long-term Debt	$ 584,000,000			$ 0