SUPPLEMENTAL GUARANTOR INFORMATION - Supplemental Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions	Dec. 28, 2019	Sep. 30, 2019
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	$ 4,194	$ 1,467
Trade accounts receivable—Net	1,025	1,068
Inventories—Net	1,294	1,233
Assets held-for-sale	0	962
Prepaid expenses and other	139	135
Total current assets	6,652	4,865
INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES	0	0
PROPERTY, PLANT AND EQUIPMENT—NET	753	757
GOODWILL	7,846	7,820
OTHER INTANGIBLE ASSETS—NET	2,737	2,744
DEFERRED INCOME TAXES	13
OTHER	155	69
TOTAL ASSETS	18,156	16,255
Current portion of long-term debt	80	80
Short-term borrowings—trade receivable securitization facility	350	350
Accounts payable	265	276
Accrued liabilities	2,655	675
Liabilities held-for-sale	0	157
Total current liabilities	3,350	1,538
LONG-TERM DEBT	17,952	16,469
DEFERRED INCOME TAXES	448	441
OTHER NON-CURRENT LIABILITIES	705	691
Total liabilities	22,455	19,139
TD GROUP STOCKHOLDERS' (DEFICIT) EQUITY	(4,303)	(2,894)
NONCONTROLLING INTERESTS	4	10
TOTAL LIABILITIES AND STOCKHOLDERS’ (DEFICIT) EQUITY	18,156	16,255
Eliminations
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	0	0
Trade accounts receivable—Net	0	0
Inventories—Net	(16)	(15)
Assets held-for-sale		0
Prepaid expenses and other	0	0
Total current assets	(16)	(15)
INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES	(35,920)	(36,081)
PROPERTY, PLANT AND EQUIPMENT—NET	0	0
GOODWILL	0	0
OTHER INTANGIBLE ASSETS—NET	0	0
DEFERRED INCOME TAXES	0
OTHER	0	0
TOTAL ASSETS	(35,936)	(36,096)
Current portion of long-term debt	0	0
Short-term borrowings—trade receivable securitization facility	0	0
Accounts payable	0	0
Accrued liabilities	0	0
Liabilities held-for-sale		0
Total current liabilities	0	0
LONG-TERM DEBT	0	0
DEFERRED INCOME TAXES	0	0
OTHER NON-CURRENT LIABILITIES	0	0
Total liabilities	0	0
TD GROUP STOCKHOLDERS' (DEFICIT) EQUITY	(35,936)	(36,096)
NONCONTROLLING INTERESTS	0	0
TOTAL LIABILITIES AND STOCKHOLDERS’ (DEFICIT) EQUITY	(35,936)	(36,096)
TransDigm Group
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	0	0
Trade accounts receivable—Net	0	0
Inventories—Net	0	0
Assets held-for-sale		0
Prepaid expenses and other	0	0
Total current assets	0	0
INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES	(4,303)	(2,894)
PROPERTY, PLANT AND EQUIPMENT—NET	0	0
GOODWILL	0	0
OTHER INTANGIBLE ASSETS—NET	0	0
DEFERRED INCOME TAXES	0
OTHER	0	0
TOTAL ASSETS	(4,303)	(2,894)
Current portion of long-term debt	0	0
Short-term borrowings—trade receivable securitization facility	0	0
Accounts payable	0	0
Accrued liabilities	0	0
Liabilities held-for-sale		0
Total current liabilities	0	0
LONG-TERM DEBT	0	0
DEFERRED INCOME TAXES	0	0
OTHER NON-CURRENT LIABILITIES	0	0
Total liabilities	0	0
TD GROUP STOCKHOLDERS' (DEFICIT) EQUITY	(4,303)	(2,894)
NONCONTROLLING INTERESTS	0	0
TOTAL LIABILITIES AND STOCKHOLDERS’ (DEFICIT) EQUITY	(4,303)	(2,894)
TransDigm Inc.
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	3,087	1,092
Trade accounts receivable—Net	0	0
Inventories—Net	55	52
Assets held-for-sale		0
Prepaid expenses and other	29	27
Total current assets	3,171	1,171
INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES	15,750	14,729
PROPERTY, PLANT AND EQUIPMENT—NET	15	17
GOODWILL	83	83
OTHER INTANGIBLE ASSETS—NET	25	25
DEFERRED INCOME TAXES	0
OTHER	20	6
TOTAL ASSETS	19,064	16,031
Current portion of long-term debt	76	76
Short-term borrowings—trade receivable securitization facility	0	0
Accounts payable	17	17
Accrued liabilities	2,158	215
Liabilities held-for-sale		0
Total current liabilities	2,251	308
LONG-TERM DEBT	17,383	15,893
DEFERRED INCOME TAXES	0	0
OTHER NON-CURRENT LIABILITIES	273	315
Total liabilities	19,907	16,516
TD GROUP STOCKHOLDERS' (DEFICIT) EQUITY	(843)	(485)
NONCONTROLLING INTERESTS	0	0
TOTAL LIABILITIES AND STOCKHOLDERS’ (DEFICIT) EQUITY	19,064	16,031
TransDigm UK [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	1	0
Trade accounts receivable—Net	0	0
Inventories—Net	0	0
Assets held-for-sale		0
Prepaid expenses and other	0	0
Total current assets	1	0
INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES	974	975
PROPERTY, PLANT AND EQUIPMENT—NET	0	0
GOODWILL	0	0
OTHER INTANGIBLE ASSETS—NET	0	0
DEFERRED INCOME TAXES	0
OTHER	0	0
TOTAL ASSETS	975	975
Current portion of long-term debt	0	0
Short-term borrowings—trade receivable securitization facility	0	0
Accounts payable	0	0
Accrued liabilities	4	12
Liabilities held-for-sale		0
Total current liabilities	4	12
LONG-TERM DEBT	492	492
DEFERRED INCOME TAXES	0	0
OTHER NON-CURRENT LIABILITIES	0	0
Total liabilities	496	504
TD GROUP STOCKHOLDERS' (DEFICIT) EQUITY	479	471
NONCONTROLLING INTERESTS	0	0
TOTAL LIABILITIES AND STOCKHOLDERS’ (DEFICIT) EQUITY	975	975
Subsidiary Guarantors
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	(15)	(12)
Trade accounts receivable—Net	161	172
Inventories—Net	899	880
Assets held-for-sale		206
Prepaid expenses and other	52	45
Total current assets	1,097	1,291
INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES	17,542	16,373
PROPERTY, PLANT AND EQUIPMENT—NET	520	513
GOODWILL	5,895	5,544
OTHER INTANGIBLE ASSETS—NET	2,025	2,064
DEFERRED INCOME TAXES	0
OTHER	92	35
TOTAL ASSETS	27,171	25,820
Current portion of long-term debt	1	1
Short-term borrowings—trade receivable securitization facility	0	0
Accounts payable	148	160
Accrued liabilities	240	237
Liabilities held-for-sale		22
Total current liabilities	389	420
LONG-TERM DEBT	42	49
DEFERRED INCOME TAXES	350	347
OTHER NON-CURRENT LIABILITIES	265	233
Total liabilities	1,046	1,049
TD GROUP STOCKHOLDERS' (DEFICIT) EQUITY	26,125	24,771
NONCONTROLLING INTERESTS	0	0
TOTAL LIABILITIES AND STOCKHOLDERS’ (DEFICIT) EQUITY	27,171	25,820
Non- Guarantor Subsidiaries
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	1,121	387
Trade accounts receivable—Net	864	896
Inventories—Net	356	316
Assets held-for-sale		756
Prepaid expenses and other	58	63
Total current assets	2,399	2,418
INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES	5,957	6,898
PROPERTY, PLANT AND EQUIPMENT—NET	218	227
GOODWILL	1,868	2,193
OTHER INTANGIBLE ASSETS—NET	687	655
DEFERRED INCOME TAXES	13
OTHER	43	28
TOTAL ASSETS	11,185	12,419
Current portion of long-term debt	3	3
Short-term borrowings—trade receivable securitization facility	350	350
Accounts payable	100	99
Accrued liabilities	253	211
Liabilities held-for-sale		135
Total current liabilities	706	798
LONG-TERM DEBT	35	35
DEFERRED INCOME TAXES	98	94
OTHER NON-CURRENT LIABILITIES	167	143
Total liabilities	1,006	1,070
TD GROUP STOCKHOLDERS' (DEFICIT) EQUITY	10,175	11,339
NONCONTROLLING INTERESTS	4	10
TOTAL LIABILITIES AND STOCKHOLDERS’ (DEFICIT) EQUITY	$ 11,185	$ 12,419