Leases - Maturity of Lease Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating Lease Liabilities, Payments Due [Abstract]
2019			$ 8.9
2019 (excluding the six months ended June 30, 2019)	$ 4.1
2020	7.7		8.0
2021	7.0		6.9
2022	6.1		5.9
2023	3.4		3.4
Thereafter	1.2		1.2
Total lease payments	29.5		$ 34.3
Less: Imputed interest	2.3
Present value of operating lease liabilities	$ 27.2	$ 29.5