Acquisitions - Quest Capital and Carl Kliem S.A. (Details) $ in Millions		1 Months Ended	3 Months Ended		12 Months Ended
	Nov. 30, 2018 USD ($) employee client	Aug. 31, 2019 USD ($)	Sep. 30, 2020 USD ($) employee	Mar. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)
Business Acquisition [Line Items]
Number of employees | employee			2,900
Bargain purchase gain			$ 81.8	$ 5.4
Quest Capital Strategies Inc [Member]
Business Acquisition [Line Items]
Purchase price		$ 1.7
Carl Kliem S.A. [Member]
Business Acquisition [Line Items]
Number of employees | employee	40
Number of clients | client	400
Purchase price	$ 2.1
Cash and cash equivalents	1.7
Receivables from clients	1.1
Property and equipment, net	0.1
Income tax receivable	0.1
Accounts payable and other accrued liabilities	0.6
Payable to clients	$ 0.2
Bargain purchase gain					$ 0.1
Operating revenues post-acquisition results of the acquired business					4.2
Net income (loss) post-acquisition results of the acquired business					$ 2.3