Goodwill and Other Intangible Assets - Summary of the Acquisition Date Fair Values of Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2019	Sep. 30, 2020	Apr. 07, 2020	Jun. 28, 2019	Apr. 04, 2019	Apr. 01, 2019	Mar. 12, 2019
Specialty Insurance Distribution (NSM)
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired		$ 275.2
Specialty Insurance Distribution (NSM) | Renewal rights
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired				$ 82.5
Embrace Pet Insurance
Acquired Finite-Lived Intangible Assets [Line Items]
Computer software, additions	$ 3.4
Embrace Pet Insurance | Specialty Insurance Distribution (NSM)
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired						$ 67.6
Kingsbridge Group Limited | Specialty Insurance Distribution (NSM)
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired			$ 125.1
Kudu
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired					$ 9.8
Other
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired							$ 37.5