Segment Information - Financial Information Related to Company's Reportable Segments (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Net sales	$ 7,267		$ 4,733	$ 14,353	$ 9,429
Segment EBITA	956		558	1,780	1,117
Corporate expenses	(240)		(110)	(433)	(197)
Amortization of intangible assets	126		20	275	40
Restructuring and impairment costs	(99)	$ (78)	(60)	(177)	(60)
Net mark-to-market adjustments on pension plans	18		0	135	0
Net financing charges	(116)		(71)	(252)	(137)
Income from continuing operations before income taxes	393		297	778	683
Power Solutions
Segment Reporting Information [Line Items]
Net sales	1,696		1,583	3,596	3,323
Segment EBITA	303		282	692	642
Building Technologies & Solutions [Member]
Segment Reporting Information [Line Items]
Net sales	5,571		3,150	10,757	6,106
Segment EBITA	653		276	1,088	475
Building Technologies & Solutions [Member] \| Building Efficiency Systems and Service North America
Segment Reporting Information [Line Items]
Net sales	1,047		1,034	1,975	2,018
Segment EBITA	90		101	165	200
Building Technologies & Solutions [Member] \| Building Efficiency Products North America
Segment Reporting Information [Line Items]
Net sales	585		546	1,128	1,103
Segment EBITA	57		47	94	80
Building Technologies & Solutions [Member] \| Building Efficiency Asia
Segment Reporting Information [Line Items]
Net sales	1,173		1,162	2,215	2,154
Segment EBITA	118		118	237	188
Building Technologies & Solutions [Member] \| Building Efficiency Rest of World [Member]
Segment Reporting Information [Line Items]
Net sales	424		408	822	831
Segment EBITA	9		10	(1)	7
Building Technologies & Solutions [Member] \| Building Technologies & Solutions Tyco [Member]
Segment Reporting Information [Line Items]
Net sales	2,342		0	4,617	0
Segment EBITA	379		0	593	0
Building Efficiency
Segment Reporting Information [Line Items]
Net sales	3,229		3,150	6,140	6,106
Segment EBITA	$ 274		$ 276	$ 495	$ 475

General expenses recorded at the Corporate segment.

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Amount of income or loss from continuing operations before income taxes and noncontrolling interests, excluding general corporate expenses, intangible asset amortization, net financing charges, significant restructuring and impairment costs, and net mark-to-market adjustments on pension and postretirement plans.

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The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

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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.

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