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	Dec. 31, 2017	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	$ 603.3	$ 605.0
Company-owned life insurance	16.0	15.9
Fair Value
Carrying amounts and estimated fair values of financial instruments not recorded at fair value
Long-term debt, including current portion	622.0	622.5
Company-owned life insurance	$ 16.0	$ 15.9