Acquisitions (Pro Forma Information) (Details) - Access Technologies - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Pro forma Net revenues	$ 923.0	$ 812.9
Pro forma Net earnings attributable to Allegion plc	128.2	94.5
Net revenues of acquiree since acquisition date	103.1
Net earnings or (loss) before income taxes of acquiree since acquisition date	7.9
Intangible Asset Amortization Expense, Net of Tax Adjustment
Pro forma Net earnings attributable to Allegion plc	1.6	(5.1)
Interest Expense, Net of Tax Adjustment
Pro forma Net earnings attributable to Allegion plc	0.0	(6.2)
Acquisition and Integration Costs, Net of Tax Adjustment
Pro forma Net earnings attributable to Allegion plc	$ 3.1	$ 2.9

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
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-Subparagraph (h)(2)
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