Merger Transaction Fair Value of Consideration Transferred (Details) $ / shares in Units, $ in Millions		12 Months Ended
	Sep. 02, 2016 USD ($) $ / shares shares	Sep. 30, 2017 USD ($) $ / shares	Sep. 30, 2016 USD ($) $ / shares shares
Tyco share consolidation ratio	0.955		0.955
Ordinary shares, par value | $ / shares	$ 1.00	$ 0.01	$ 0.01
Business Combination, Consideration Transferred per Share For Share Election | $ / shares	$ 5.7293
Business Combination, Consideration Transferred, Shares, For Share Election | shares	0.8357
Business Combination, Consideration Transferred per Share | $ / shares	$ 34.88		$ 34.88
Cash consideration paid to JCI Inc. shareholders | $	$ 3,864	$ 3,900	$ 3,864
Percent Ownership by Shareholders of Acquiror Subsequent to Acquisition	56.00%
Percent Ownership by Shareholders of Acquiree Subsequent to Acquisition	44.00%
Total fair value of consideration transferred | $	$ 19,671	$ 19,700
Fair value of Tyco equity awards | $	224
Fair Value of Acquiree Equity Awards not Earned as of Merger Date | $	$ 101
Number of Tyco shares outstanding at September 2, 2016 | shares	427,181,743		427,181,743
Tyco ordinary shares outstanding following the share consolidation and immediately prior to the Merger | shares	407,958,565		407,958,565
JCI Inc. converted share price (1) | $ / shares	$ 47.67
Fair value of equity portion of the Merger consideration | $	$ 19,447
Acquiror Closing Share Price | $ / shares	$ 45.45
JCI Inc. market capitalization at Merger date | $	$ 29,012
Reduction in shares due to cash consideration paid by Tyco | shares	110,800,000		(110,800,000)
Tyco Merger [Member]
Ordinary shares, par value | $ / shares	$ 1.00