Employees - Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Service cost	$ 1.2	$ 0.4	$ 1.2
Interest cost	$ 2.7	5.2	2.7
Expected return on plan assets		(8.0)	(2.7)
Recognition of gain due to settlement		(0.1)	0.0
Recognition of gain due to curtailment		(2.4)	(6.1)
Net periodic benefit cost		$ (4.9)	$ (4.9)