Consolidated Statements of Cash Flow Cash, Cash Equivalents, and Restricted Cash - USD ($) $ in Millions	Jun. 30, 2020	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents	$ 263.1	$ 399.0	$ 64.4
Short-term restricted cash included in other current assets	1.8		0.6
Total cash, cash equivalents, and restricted cash shown in the Consolidated Statements of Cash Flows	$ 264.9	$ 399.4	$ 65.0	$ 56.5