Related Party Transactions - Summary of Activity Related to Agreements with Related Party (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Related Party Transaction [Line Items]
Processing fee incurred	$ 87.5	$ 73.1	$ 165.6	$ 135.6
Earnings from equity investments	3.7	1.7	6.4	3.3
Distributions received from equity investments			7.4	4.4
LM4
Related Party Transaction [Line Items]
Processing fee incurred	$ 8.6	$ 5.8	$ 15.4	$ 10.8
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Earnings from equity investments	$ 3.7	$ 1.7	$ 6.4	$ 3.3
Distributions received from equity investments	$ 3.9	$ 1.8	$ 7.4	$ 4.4

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