Debt - Maturities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Annual maturities of debt:
2019	$ 18.5
2020	112.3
2021	1.7
2022	106.0
2023	1.1
Thereafter	101.5
Total debt	341.1	$ 415.6
Interest expense	$ 12.6	$ 15.4	$ 13.2