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	Mar. 31, 2018	Jun. 30, 2017
Carrying Value
Carrying amounts and estimated fair values of financial instruments not recorded at fair value
Long-term debt, including current portion	$ 601.3	$ 605.0
Company-owned life insurance	15.8	15.9
Fair Value
Carrying amounts and estimated fair values of financial instruments not recorded at fair value
Long-term debt, including current portion	610.0	622.5
Company-owned life insurance	$ 15.8	$ 15.9