Income Taxes Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Deferred tax assets, investments	$ 54.0	$ 55.3
Deferred tax assets, operating loss carryforwards	24.4	25.7
Deferred tax assets, tax credit carryforwards	15.6	12.9
Deferred tax assets, tax deferred expense, compensation and benefits	8.4	7.9
Deferred tax assets, tax deferred expense, reserves and accruals	2.2	1.1
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Deferred Rent	12.0	11.5
Deferred Tax Assets, Property, Plant and Equipment	11.6	12.1
Deferred tax assets, other	7.5	7.9
Deferred tax assets, valuation allowance	(81.2)	(71.2)
Deferred tax assets, net of valuation allowance	55.8	65.6
Deferred tax liabilities, property, plant and equipment	(66.0)	(67.8)
Deferred Tax Liabilities, Leasing Arrangements	(11.0)	(10.6)
Deferred tax liabilities, gross	(77.0)	(78.4)
Deferred tax liabilities, net	(21.2)	(12.8)
Deferred Tax Asset, Interest Carryforward	$ 1.3	$ 2.4