Goodwill and Other Intangible Assets - Summary of the Acquisition Date Fair Values of Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	Aug. 06, 2021	May 01, 2021	Jan. 01, 2021	Jul. 02, 2020	Apr. 07, 2020
Specialty Insurance Distribution (NSM)
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired	$ 187.4				$ 187.4
Kingsbridge | Specialty Insurance Distribution (NSM)
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired					$ 131.7
J.C. Taylor | Specialty Insurance Distribution (NSM)
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired	$ 55.7
Ark
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired			$ 292.5
Other
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired		$ 30.6		$ 30.6