Related Party Transactions - Summary of Activity Related to Agreements with Related Party (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Earnings from equity investments	$ 10.6	$ 10.3	$ 3.4
Distributions received from equity investments	17.4	9.7
LM4
Related Party Transaction [Line Items]
Processing fee incurred	27.7	25.6	6.3
Earnings from equity investments	10.6	10.3	$ 3.4
Distributions received from equity investments	$ 17.4	$ 9.7

Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities.

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