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

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

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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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.

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

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

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

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Amount of long-term debt classified as other.

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Debt and Financing Arrangements Long-Term Debt (Details)	Sep. 30, 2021 USD ($)	Sep. 30, 2021 EUR (€)	Sep. 30, 2021 JPY (¥)	Sep. 30, 2020 USD ($)
Debt Instrument [Line Items]
Other Long-term Debt	$ 8,000,000			$ 8,000,000
Long-term Debt and Capital Lease Obligations, Including Current Maturities	7,764,000,000			7,822,000,000
Less: current portion	226,000,000			262,000,000
Debt Issuance Costs, Net	32,000,000			34,000,000
Net long-term debt	$ 7,506,000,000			7,526,000,000
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	$ 25,000,000			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
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	$ 0			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	$ 0			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	$ 0			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	$ 0			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 \| €		€ 846,000,000
Long-term Debt	$ 980,000,000			1,039,000,000
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	$ 496,000,000			503,000,000
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	$ 63,000,000			64,000,000
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	$ 510,000,000			516,000,000
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	$ 560,000,000			564,000,000
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	$ 223,000,000			237,000,000
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	$ 577,000,000			583,000,000
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			623,000,000
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	$ 578,000,000			584,000,000
Two Point Zero Percent Due Two Thousand Thirty One \| Johnson Controls International plc (JCI) and Tyco Fire & Security Finance S.C.A. (TFSCA)
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.00%	2.00%	2.00%
Debt instrument, face amount	$ 500,000,000
Long-term Debt	$ 496,000,000			$ 0