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, 2019	Jun. 30, 2019
Carrying Value
Carrying amounts and estimated fair values of financial instruments not recorded at fair value
Long-term debt	$ 550.9	$ 550.6
Company-owned life insurance	18.5	17.9
Fair Value
Carrying amounts and estimated fair values of financial instruments not recorded at fair value
Long-term debt	566.2	560.6
Company-owned life insurance	$ 18.5	$ 17.9