CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) shares in Millions, $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2017	Mar. 31, 2018	Sep. 30, 2018	Mar. 31, 2017
Restricted cash	$ 40.2	$ 42.1	$ 40.0	$ 0.0
2017 Junior Convertible Debt | Long-term Debt
Proceeds from issuance of senior subordinated convertible debentures, net of issuance costs	$ 111.3
2007 Junior Convertible Debt | Long-term Debt
Stock issued during period, exchange of convertible securities (in shares)	3.2
Extinguishment of debt	$ 111.3	$ 32.5