Summary of Significant Accounting Policies - Business Acquisition (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2022	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Apr. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Payments to Acquire Businesses, Net of Cash Acquired		$ 271.5	$ 24.5	$ 9.7
Scehdule of Business Information [Line Items]
Deferred income taxes, net		141.1	155.3
Payments to Acquire Businesses, Net of Cash Acquired		271.5	24.5	$ 9.7
Vidler Water Resources, Inc.
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Payments to Acquire Businesses, Net of Cash Acquired	$ 290.5
Scehdule of Business Information [Line Items]
Business acquisition, deferred income tax valuation allowance acquired					$ 15.8
Business acquisition, cash and cash equivalents acquired					19.0
Deferred income taxes, net					14.8
Business acquisition, intangible and other assets acquired		$ 286.6	$ 0.0		280.1
Business acquisition, total assets acquired					313.9
Business acquisition, other liabilities acquired					5.4
Business acquisition, total liabilities acquired					5.4
Business acquisition, noncontrolling interest					18.0
Business acquisition, net assets acquired					$ 290.5
Business Acquisition, Share Price					$ 15.75
Payments to Acquire Businesses, Net of Cash Acquired	$ 290.5