Income Taxes - Deferred Income Taxes, Net (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets
Allowances and other reserves	$ 2.2	$ 6.3
Net operating loss carryforwards	82.1	223.1
Research and development tax credits		4.1
Interest hedging		2.0
Other	1.0	1.4
Total deferred tax assets	85.3	236.9
Less: valuation allowance	(35.5)	(30.8)
Deferred tax asset	49.8	206.1
Deferred tax liabilities
Depreciation and amortization	(145.8)	(206.3)
Franchise operating rights	(161.5)	(198.6)
Debt issuance costs		(1.8)
Total deferred tax liabilities	(307.3)	(406.7)
Net deferred tax liabilities	$ (257.5)	$ (200.6)