Related Party Transactions - Summary of Activity Related to Agreements with Related Party (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Related Party Transaction [Line Items]
Processing fee incurred	$ 78.1	$ 62.5
Earnings from equity investments	2.7	1.6
Distributions received from equity investments	3.5	2.6
LM4
Related Party Transaction [Line Items]
Processing fee incurred	$ 6.8	$ 5.0
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Earnings from equity investments	$ 2.7	$ 1.6
Distributions received from equity investments	$ 3.5	$ 2.6

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