Investments (Other Investments) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018	Mar. 31, 2018
Equity Method Investments, and Investments in Debt and Equity Securities [Abstract]
Investments in equity securities measured at fair value, amount	$ 1.0		$ 1.0			$ 7.3
Unrealized losses on equity securities held at reporting date	3.6	$ 0.0	6.4	$ 0.0
Equity securities without readily determinable fair value, amount	$ 0.5		$ 0.5		$ 0.0	$ 30.6