Debt - Maturities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Annual maturities of debt:
2017	$ 20.1
2018	0.1
2019	15.0
2020	171.0
Thereafter	205.5
Total debt	411.7	$ 265.8
Interest expense	$ 13.2	$ 13.0	$ 13.3