Income Taxes - Deferred tax liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Non-current deferred income tax (assets) liabilities:
Allowances and other reserves	$ (6.8)	$ (7.1)
Net operating loss carryforwards	(203.7)	(172.8)
Depreciation and amortization	183.9	140.5
Franchise operating rights	202.0	204.7
Interest hedging	(4.8)
Debt issuance costs	2.5	3.2
State income tax	(0.9)	(1.9)
Other	(6.4)	(4.1)
Valuation allowance	26.7	30.4
Total net deferred tax liabilities	$ 192.5	$ 192.9