Debt and Financing Arrangements Long-Term Debt (Details)	Sep. 30, 2017 USD ($)	Sep. 30, 2017 EUR (€)	Sep. 30, 2016 USD ($)	Sep. 30, 2016 EUR (€)
Debt Instrument [Line Items]
Other Long-term Debt	$ 47,000,000		$ 39,000,000
Capital lease obligations	19,000,000		24,000,000
Long-term Debt and Capital Lease Obligations, Including Current Maturities	12,403,000,000		15,234,000,000
Less: current portion	394,000,000		628,000,000
Debt Issuance Costs, Line of Credit Arrangements, Gross	45,000,000		74,000,000
Current portion of long-term debt	0		38,000,000
Long-term debt	0		3,441,000,000
Net long-term debt	11,964,000,000		11,053,000,000
Tyco International Holding S.a.r.L. (TSarL) [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 4,000,000,000
7.125 % Due in 2017 | Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			7.125%	7.125%
Debt instrument, face amount			$ 150,000,000
Long-term Debt	0		$ 149,000,000
Two Point Six Percent Due Two Thousand Seventeen | Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.60%	2.60%
Debt instrument, face amount			$ 400,000,000
Long-term Debt	0		$ 404,000,000
Two Point Three Five Five Percent Due Two Thousand Seventeen | Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.355%	2.355%
Debt instrument, face amount			$ 46,000,000
Long-term Debt	$ 0		$ 46,000,000
1.4% Due in 2018 | Johnson Controls Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.40%	1.40%	1.40%	1.40%
Debt instrument, face amount	$ 41,000,000		$ 300,000,000
Long-term Debt	$ 42,000,000		301,000,000
1.4% Due in 2018 | Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.40%	1.40%
Debt instrument, face amount	$ 259,000,000
Long-term Debt	$ 259,000,000		0
Three Point Seven Five Percent Due in Two Thousand Eighteen [Member] | Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.75%	3.75%
Debt instrument, face amount	$ 49,000,000
Long-term Debt	$ 49,000,000		$ 0
Three Point Seven Five Percent Due in Two Thousand Eighteen [Member] | Tyco International Finance S.A. (TIFSA) [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.75%	3.75%	3.75%	3.75%
Debt instrument, face amount	$ 18,000,000		$ 67,000,000
Long-term Debt	$ 18,000,000		$ 69,000,000
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%	5.00%
Debt instrument, face amount	$ 47,000,000		$ 500,000,000
Long-term Debt	$ 47,000,000		499,000,000
5.0 % Due in 2020 | Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.00%	5.00%
Debt instrument, face amount	$ 452,000,000
Long-term Debt	$ 452,000,000		$ 0
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%	4.25%
Debt instrument, face amount	$ 53,000,000		$ 500,000,000
Long-term Debt	$ 53,000,000		498,000,000
4.25% Due in 2021 | Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.25%	4.25%
Debt instrument, face amount	$ 447,000,000
Long-term Debt	$ 446,000,000		$ 0
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%	3.75%
Debt instrument, face amount	$ 22,000,000		$ 450,000,000
Long-term Debt	$ 22,000,000		448,000,000
3.75 % Due in 2022 | Johnson Controls International plc [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.75%	3.75%
Debt instrument, face amount	$ 428,000,000
Long-term Debt	$ 427,000,000		0
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%
Debt instrument, face amount	$ 35,000,000
Long-term Debt	$ 38,000,000		$ 0
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%	4.625%
Debt instrument, face amount	$ 7,000,000		$ 42,000,000
Long-term Debt	$ 8,000,000		46,000,000
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%
Debt instrument, face amount | €		€ 1,000,000,000
Long-term Debt	$ 1,171,000,000		$ 0
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%	3.625%
Debt instrument, face amount	$ 31,000,000		$ 500,000,000
Long-term Debt	$ 31,000,000		500,000,000
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%
Debt instrument, face amount	$ 468,000,000
Long-term Debt	$ 468,000,000		$ 0
Three Point Five Percent Due Two Thousand Twenty Four [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.50%	3.50%
Debt instrument, face amount | €		€ 1,000,000,000
Three Point Five Percent Due Two Thousand Twenty Four [Member] | Adient
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.50%	3.50%
Debt instrument, face amount | €				€ 1,000,000,000
Long-term Debt	$ 0		$ 1,119,000,000
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%
Debt instrument, face amount | €		€ 423,000,000
Long-term Debt	$ 510,000,000		$ 0
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%	1.375%
Debt instrument, face amount | €		€ 58,000,000		€ 500,000,000
Long-term Debt	$ 70,000,000		$ 571,000,000
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%
Debt instrument, face amount	$ 698,000,000
Long-term Debt	$ 763,000,000		$ 0
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%	3.90%
Debt instrument, face amount	$ 51,000,000		$ 750,000,000
Long-term Debt	$ 53,000,000		$ 824,000,000
Four Point Eight Seven Five Percent Due Two Thousand Twenty Six [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.875%	4.875%
Long-term Debt	$ 900,000,000
Four Point Eight Seven Five Percent Due Two Thousand Twenty Six [Member] | Adient
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			4.875%	4.875%
Debt instrument, face amount			$ 900,000,000
Long-term Debt	$ 0		$ 900,000,000
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%	6.00%
Debt instrument, face amount	$ 8,000,000		$ 400,000,000
Long-term Debt	$ 8,000,000		396,000,000
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%
Debt instrument, face amount	$ 392,000,000
Long-term Debt	$ 388,000,000		$ 0
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%	5.70%
Debt instrument, face amount	$ 30,000,000		$ 300,000,000
Long-term Debt	$ 30,000,000		299,000,000
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%
Debt instrument, face amount	$ 270,000,000
Long-term Debt	$ 269,000,000		$ 0
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%	5.25%
Debt instrument, face amount	$ 8,000,000		$ 250,000,000
Long-term Debt	$ 8,000,000		250,000,000
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%
Debt instrument, face amount	$ 242,000,000
Long-term Debt	$ 242,000,000		$ 0
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%	4.625%
Debt instrument, face amount	$ 6,000,000		$ 450,000,000
Long-term Debt	$ 6,000,000		447,000,000
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%
Debt instrument, face amount	$ 445,000,000
Long-term Debt	$ 441,000,000		0
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%
Debt instrument, face amount	$ 727,000,000
Long-term Debt	$ 872,000,000		$ 0
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%	5.125%
Debt instrument, face amount	$ 23,000,000		$ 750,000,000
Long-term Debt	$ 23,000,000		$ 903,000,000
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%	6.95%
Debt instrument, face amount	$ 4,000,000		$ 125,000,000
Long-term Debt	$ 4,000,000		125,000,000
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%
Debt instrument, face amount	$ 121,000,000
Long-term Debt	$ 121,000,000		0
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%
Debt instrument, face amount	$ 500,000,000
Long-term Debt	$ 495,000,000		$ 0
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%	4.95%
Debt instrument, face amount	$ 15,000,000		$ 450,000,000
Long-term Debt	$ 15,000,000		449,000,000
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%
Debt instrument, face amount	$ 435,000,000
Long-term Debt	$ 434,000,000		$ 0
LIBOR plus One Point Five Percent Due in Two Thousand Twenty [Member] | Tyco International Holding S.a.r.L. (TSarL) [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.50%	1.50%	1.50%	1.50%
Long-term Debt	$ 3,700,000,000
LIBOR plus One Point Zero Zero Five Percent Due Two Thousand Twenty One [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			1.005%	1.005%
LIBOR plus One Point Zero Zero Five Percent Due Two Thousand Twenty One [Member] | Adient
Debt Instrument [Line Items]
Long-term Debt	0		$ 1,500,000,000
Foreign Currency Denominated Debt [Member] | Euro Member Countries, Euro
Debt Instrument [Line Items]
Long-term Debt	43,000,000		61,000,000
Foreign Currency Denominated Debt [Member] | Japan, Yen
Debt Instrument [Line Items]
Long-term Debt	311,000,000		367,000,000
LIBOR plus One Point Five Percent Due in Two Thousand Twenty [Member] | Tyco International Holding S.a.r.L. (TSarL) [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 3,700,000,000		$ 4,000,000,000