Commitments and Contingencies - Lease Commitments and Income (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2015
Operating Leased Assets [Line Items]
Rent expense	$ 1.8	$ 20.7	$ 21.2	$ 18.5
Lease income	$ 0.5	6.4	$ 6.5	$ 6.3
Future Minimum Rental Commitments
2018		15.1
2019		14.6
2020		14.1
2021		14.2
2022		13.2
Thereafter		23.9
Total		95.1
Future Minimum Rental Income
2018		4.8
2019		2.5
2020		0.7
2021		0.7
2022		0.2
Thereafter		0.0
Total		$ 8.9
Minimum
Operating Leased Assets [Line Items]
Lease renewal options range		1 year
Maximum
Operating Leased Assets [Line Items]
Lease renewal options range		5 years