Income Taxes, Deferred Tax Liabilities and Assets (Details) - USD ($) $ in Millions		Dec. 31, 2020	Mar. 05, 2020	Dec. 31, 2019
Deferred tax liabilities:
Attributable to investment in OTA		$ 356.6	$ 439.7	$ 0.0
Attributable to property, plant and equipment		106.4		100.2
Attributable to investments in other entities		4.1		3.3
Total deferred tax liabilities		467.1		103.5
Less: deferred tax assets:
Net operating loss carryovers	[1]	0.1		0.1
Temporary differences related to Texas Margin Tax		2.3		3.0
Total deferred tax assets		2.4		3.1
Total net deferred tax liabilities		$ 464.7		$ 100.4

[1] These losses expire in various years between 2021 and 2037 and are subject to limitations on their utilization.