Related Party Transactions - Summary of Activity Related to Agreements with Related Party (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Related Party Transaction [Line Items]
Processing fee incurred	$ 347.3	$ 313.0	$ 279.6
Earnings from equity investments	14.0	7.7	5.3
Distributions received from equity investments	17.2	11.4	13.0
LM4
Related Party Transaction [Line Items]
Processing fee incurred	$ 32.6	$ 24.0	$ 20.5
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Earnings from equity investments	$ 14.0	$ 7.7	$ 5.3
Distributions received from equity investments	$ 17.2	$ 11.4	$ 13.0

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