Income Taxes, Benefit from (provision for) income taxes (Details) - USD ($) $ in Millions			1 Months Ended	3 Months Ended
		Mar. 05, 2020	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Components of Benefit From (Provision For) Income Taxes:
Texas Margin Tax	[1]			$ (3.3)	$ (7.7)
Other				(0.4)	(0.3)
Benefit from (provision for) income taxes				(10.0)	179.2
OTA Holdings, Inc. [Member]
Components of Benefit From (Provision For) Income Taxes:
Benefit from (provision for) income taxes		$ 72.2	$ 115.0	$ (6.3)	$ 187.2

[1] Although the Texas Margin Tax is not considered a state income tax, it has the characteristics of an income tax since it is determined by applying a tax rate to a base that considers our Texas-sourced revenues and expenses.