Fair Value Measurements - Schedule of carrying amounts and estimated fair values of financial instruments not recorded at fair value in the financial statements (Details) - Level 2 - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020
Carrying Value
Carrying amounts and estimated fair values of financial instruments not recorded at fair value
Long-term debt	$ 693.8	$ 551.8
Company-owned life insurance	19.4	18.9
Fair Value
Carrying amounts and estimated fair values of financial instruments not recorded at fair value
Long-term debt	732.3	551.1
Company-owned life insurance	$ 19.4	$ 18.9