Consolidated Statements of Cash Flow Cash, Cash Equivalents, and Restricted Cash - USD ($) $ in Millions	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents	$ 374.0	$ 399.0	$ 58.6
Short-term restricted cash included in other current assets	0.4		0.8
Total cash, cash equivalents, and restricted cash shown in the Consolidated Statements of Cash Flows	$ 374.4	$ 399.4	$ 59.4	$ 56.5