Business Segment Information Narrative (Details) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) segment	Jun. 30, 2024 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| segment			2
Net revenues	$ 1,022.0	$ 965.6	$ 1,963.9	$ 1,859.5
Operating Income (Loss)	219.7	209.0	416.1	381.1
Operating Segments
Operating Income (Loss)	252.3	232.0	475.4	432.0
Operating Segments \| Allegion Americas
Net revenues	821.5	770.7	1,579.3	1,480.0
Operating Income (Loss)	236.6	214.3	448.0	401.3
Operating Segments \| Allegion International
Net revenues	200.5	194.9	384.6	379.5
Operating Income (Loss)	$ 15.7	$ 17.7	$ 27.4	$ 30.7

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details