Business Segment Information Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) segment	Sep. 30, 2022 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment			2
Net revenues	$ 917.9	$ 913.7	$ 2,753.4	$ 2,410.4
Operating Income (Loss)	193.1	162.9	548.7	427.0
Operating Segments
Operating Income (Loss)	215.9	193.3	622.4	501.8
Operating Segments | Allegion Americas
Net revenues	740.9	741.9	2,209.0	1,851.1
Operating Income (Loss)	200.2	178.5	582.2	454.4
Operating Segments | Allegion International
Net revenues	177.0	171.8	544.4	559.3
Operating Income (Loss)	$ 15.7	14.8	$ 40.2	47.4
Operating Segments | Allegion International | Global Portable Security Brand's Segment Reclassification
Net revenues		5.2		16.5
Operating Income (Loss)		$ (0.1)		$ 1.5