TIFSA Condensed Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2016
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	$ 268	$ 321	$ 412	$ 579
Accounts receivable - net	6,679	6,666
Inventories	3,565	3,209
Intercompany receivables	0	0
Assets held for sale	22	189
Other current assets	1,737	1,907
Current assets	12,271	12,292
Property, plant and equipment - net	6,235	6,121
Goodwill	19,806	19,688
Other intangible assets - net	6,625	6,741
Investments in partially-owned affiliates	1,294	1,191
Investments in affiliates	0	0
Intercompany loans receivable	0	0
Noncurrent assets held for sale	0	1,920
Other noncurrent assets	3,721	3,931
Total assets	49,952	51,884
Short-term debt	1,111	1,214
Current portion of long-term debt	25	394
Accounts payable	4,250	4,271
Accrued compensation and benefits	866	1,071
Deferred revenue	1,543	1,279
Liabilities held for sale	0	72
Intercompany payables	0	0
Other current liabilities	3,197	3,553
Current liabilities	10,992	11,854
Long-term debt	10,962	11,964
Pension and postretirement benefits	864	947
Intercompany loans payable	0	0
Noncurrent liabilities held for sale	0	173
Other noncurrent liabilities	5,019	5,368
Long-term liabilities	16,845	18,452
Redeemable noncontrolling interests	235	211
Ordinary shares	9	9
Ordinary shares held in treasury	(946)	(710)
Other shareholders' equity	21,811	21,148
Shareholders' equity attributable to Johnson Controls	20,874	20,447
Nonredeemable noncontrolling interest	1,006	920
Total equity	21,880	21,367
Total liabilities and equity	49,952	51,884
Consolidation, Eliminations [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	(1,490)	(886)	(361)	0
Accounts receivable - net	0	0
Inventories	0	0
Intercompany receivables	(25,709)	(7,837)
Assets held for sale	0	0
Other current assets	0	0
Current assets	(27,199)	(8,723)
Property, plant and equipment - net	0	0
Goodwill	0	0
Other intangible assets - net	0	0
Investments in partially-owned affiliates	0	0
Investments in affiliates	(94,975)	(72,213)
Intercompany loans receivable	(15,980)	(33,888)
Noncurrent assets held for sale		0
Other noncurrent assets	0	0
Total assets	(138,154)	(114,824)
Short-term debt	(1,490)	(886)
Current portion of long-term debt	0	0
Accounts payable	0	0
Accrued compensation and benefits	0	0
Deferred revenue	0	0
Liabilities held for sale		0
Intercompany payables	(25,709)	(7,837)
Other current liabilities	0	0
Current liabilities	(27,199)	(8,723)
Long-term debt	0	0
Pension and postretirement benefits	0	0
Intercompany loans payable	(15,980)	(33,888)
Noncurrent liabilities held for sale		0
Other noncurrent liabilities	0	0
Long-term liabilities	(15,980)	(33,888)
Redeemable noncontrolling interests	0	0
Ordinary shares	0	0
Ordinary shares held in treasury	0	0
Other shareholders' equity	(94,975)	(72,213)
Shareholders' equity attributable to Johnson Controls	(94,975)	(72,213)
Nonredeemable noncontrolling interest	0	0
Total equity	(94,975)	(72,213)
Total liabilities and equity	(138,154)	(114,824)
Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	0	0	3	11
Accounts receivable - net	0	0
Inventories	0	0
Intercompany receivables	48	1,580
Assets held for sale	0	0
Other current assets	11	14
Current assets	59	1,594
Property, plant and equipment - net	0	0
Goodwill	243	243
Other intangible assets - net	0	0
Investments in partially-owned affiliates	0	0
Investments in affiliates	39,838	19,487
Intercompany loans receivable	0	17,908
Noncurrent assets held for sale		0
Other noncurrent assets	63	56
Total assets	40,203	39,288
Short-term debt	2,163	1,476
Current portion of long-term debt	0	307
Accounts payable	1	0
Accrued compensation and benefits	1	4
Deferred revenue	0	0
Liabilities held for sale		0
Intercompany payables	3,361	4,236
Other current liabilities	303	324
Current liabilities	5,829	6,347
Long-term debt	8,812	7,806
Pension and postretirement benefits	0	0
Intercompany loans payable	4,688	4,688
Noncurrent liabilities held for sale		0
Other noncurrent liabilities	0	0
Long-term liabilities	13,500	12,494
Redeemable noncontrolling interests	0	0
Ordinary shares	9	9
Ordinary shares held in treasury	(946)	(710)
Other shareholders' equity	21,811	21,148
Shareholders' equity attributable to Johnson Controls	20,874	20,447
Nonredeemable noncontrolling interest	0	0
Total equity	20,874	20,447
Total liabilities and equity	40,203	39,288
Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	304	107	0	0
Accounts receivable - net	0	0
Inventories	0	0
Intercompany receivables	2,206	1,732
Assets held for sale	0	0
Other current assets	2	0
Current assets	2,512	1,839
Property, plant and equipment - net	0	0
Goodwill	0	0
Other intangible assets - net	0	0
Investments in partially-owned affiliates	0	0
Investments in affiliates	33,681	31,594
Intercompany loans receivable	4,140	4,140
Noncurrent assets held for sale		0
Other noncurrent assets	0	0
Total assets	40,333	37,573
Short-term debt	9	0
Current portion of long-term debt	0	0
Accounts payable	0	0
Accrued compensation and benefits	0	0
Deferred revenue	0	0
Liabilities held for sale		0
Intercompany payables	19,459	1,055
Other current liabilities	13	2
Current liabilities	19,481	1,057
Long-term debt	0	0
Pension and postretirement benefits	0	0
Intercompany loans payable	0	17,908
Noncurrent liabilities held for sale		0
Other noncurrent liabilities	0	0
Long-term liabilities	0	17,908
Redeemable noncontrolling interests	0	0
Ordinary shares	0	0
Ordinary shares held in treasury	0	0
Other shareholders' equity	20,852	18,608
Shareholders' equity attributable to Johnson Controls	20,852	18,608
Nonredeemable noncontrolling interest	0	0
Total equity	20,852	18,608
Total liabilities and equity	40,333	37,573
Subsidiary Issuer [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	161	382	288	244
Accounts receivable - net	0	0
Inventories	0	0
Intercompany receivables	365	55
Assets held for sale	0	0
Other current assets	2	1
Current assets	528	438
Property, plant and equipment - net	0	0
Goodwill	32	32
Other intangible assets - net	0	0
Investments in partially-owned affiliates	0	0
Investments in affiliates	21,456	21,132
Intercompany loans receivable	2,836	2,836
Noncurrent assets held for sale		0
Other noncurrent assets	3	7
Total assets	24,855	24,445
Short-term debt	0	0
Current portion of long-term debt	0	18
Accounts payable	0	0
Accrued compensation and benefits	0	0
Deferred revenue	0	0
Liabilities held for sale		0
Intercompany payables	2,031	1,886
Other current liabilities	27	24
Current liabilities	2,058	1,928
Long-term debt	155	152
Pension and postretirement benefits	0	0
Intercompany loans payable	4,316	4,316
Noncurrent liabilities held for sale		0
Other noncurrent liabilities	24	24
Long-term liabilities	4,495	4,492
Redeemable noncontrolling interests	0	0
Ordinary shares	0	0
Ordinary shares held in treasury	0	0
Other shareholders' equity	18,302	18,025
Shareholders' equity attributable to Johnson Controls	18,302	18,025
Nonredeemable noncontrolling interest	0	0
Total equity	18,302	18,025
Total liabilities and equity	24,855	24,445
Non-Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	1,293	718	$ 482	$ 324
Accounts receivable - net	6,679	6,666
Inventories	3,565	3,209
Intercompany receivables	23,090	4,470
Assets held for sale	22	189
Other current assets	1,722	1,892
Current assets	36,371	17,144
Property, plant and equipment - net	6,235	6,121
Goodwill	19,531	19,413
Other intangible assets - net	6,625	6,741
Investments in partially-owned affiliates	1,294	1,191
Investments in affiliates	0	0
Intercompany loans receivable	9,004	9,004
Noncurrent assets held for sale		1,920
Other noncurrent assets	3,655	3,868
Total assets	82,715	65,402
Short-term debt	429	624
Current portion of long-term debt	25	69
Accounts payable	4,249	4,271
Accrued compensation and benefits	865	1,067
Deferred revenue	1,543	1,279
Liabilities held for sale		72
Intercompany payables	858	660
Other current liabilities	2,854	3,203
Current liabilities	10,823	11,245
Long-term debt	1,995	4,006
Pension and postretirement benefits	864	947
Intercompany loans payable	6,976	6,976
Noncurrent liabilities held for sale		173
Other noncurrent liabilities	4,995	5,344
Long-term liabilities	14,830	17,446
Redeemable noncontrolling interests	235	211
Ordinary shares	0	0
Ordinary shares held in treasury	0	0
Other shareholders' equity	55,821	35,580
Shareholders' equity attributable to Johnson Controls	55,821	35,580
Nonredeemable noncontrolling interest	1,006	920
Total equity	56,827	36,500
Total liabilities and equity	$ 82,715	$ 65,402