Income Taxes (Details) - USD ($) $ in Millions			3 Months Ended		4 Months Ended	6 Months Ended
		Mar. 05, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
OTA Deferred Tax Liability:
Liquidity Option liability		$ 511.9
Current portion of income tax benefit (provision):
Federal			$ (0.2)	$ (2.2)		$ 0.6	$ (2.3)
State			(11.5)	(4.1)		(16.6)	(8.7)
Foreign			0.0	0.0		(1.1)	(0.2)
Total current portion			(11.7)	(6.3)		(17.1)	(11.2)
Deferred portion of income tax benefit (provision):
Federal		67.8	(6.3)	(46.4)		(12.2)	126.4
State		4.4	(13.2)	(7.0)		(11.9)	4.3
Foreign			0.0	0.0		0.0	0.0
Total deferred portion			(19.5)	(53.4)		(24.1)	130.7
Total benefit from (provision for) income taxes			(31.2)	(59.7)		(41.2)	119.5
Deferred tax liabilities:
Attributable to investment in OTA			369.9			369.9		$ 356.6
Attributable to property, plant and equipment			117.8			117.8		106.4
Attributable to investments in other entities			4.2			4.2		4.1
Other			13.5			13.5		0.0
Total deferred tax liabilities			505.4			505.4		467.1
Less: deferred tax assets:
Net operating loss carryovers	[1]		6.3			6.3		0.1
Temporary differences related to Texas Margin Tax			3.0			3.0		2.3
Total deferred tax assets			9.3			9.3		2.4
Total net deferred tax liabilities before valuation allowance			496.1			496.1		464.7
Less: Valuation allowance on deferred tax assets			6.2			6.2		0.0
Total net deferred tax liabilities			502.3			502.3		$ 464.7
Net operating loss carryover subject to expiration			0.1			0.1
Net operating loss carryover not subject to expiration			6.2			6.2
OTA Holdings, Inc. [Member]
Deferred portion of income tax benefit (provision):
Total benefit from (provision for) income taxes		72.2	$ (7.0)	$ (50.5)	$ 64.5	$ (13.3)	$ 136.7
Deferred tax liabilities:
Total deferred tax liabilities		$ 439.7

[1] Of the loss amount presented for June 30, 2021, $0.1 million expires in various years between 2021 and 2037.  The remaining $6.2 million has an indefinite carryover period.  All losses are subject to limitations on their utilization.