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, 2019	Jun. 30, 2018
Carrying Value
Carrying amounts and estimated fair values of financial instruments not recorded at fair value
Long-term debt	$ 549.0	$ 545.7
Company-owned life insurance	16.8	16.4
Fair Value
Carrying amounts and estimated fair values of financial instruments not recorded at fair value
Long-term debt	562.0	558.3
Company-owned life insurance	$ 16.8	$ 16.4