Income Taxes - Deferred Income Taxes, Net (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Non-current deferred income tax (assets) liabilities:
Allowances and other reserves	$ 6.3	$ 6.8
Net operating loss carryforwards	223.1	203.7
Research and development tax credits	4.1
Interest hedging	2.0	4.8
Other	1.4	7.1
Total deferred tax assets	236.9	222.4
Less: valuation allowance	(30.8)	(26.5)
Deferred tax asset	206.1	195.9
Depreciation and amortization	(206.3)	(183.9)
Franchise operating rights	(198.6)	(202.0)
Debt issuance costs	(1.8)	(2.5)
Total deferred tax liabilities	(406.7)	(388.4)
Net deferred tax liabilities	$ (200.6)	$ (192.5)