Liabilities - Other Liabilities (Details) - USD ($) $ in Millions	48 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Other liabilities
Contributions to deferred compensation plan	$ 0.0
Accrued and deferred deposit payments	3.5	$ 3.5
Other Assets
Other liabilities
Deferred compensation plan assets	2.5	2.4
Accrued expenses and other current liabilities
Other liabilities
Accrued and deferred deposit payments	1.7	1.7
Other Liabilities
Other liabilities
Deferred compensation plan liabilities		2.5
Medical and dental benefits	1.9
Asset retirement obligations	2.7
Income taxes payable		1.4
Accrued and deferred deposit payments	$ 1.8	$ 1.8