Retirement Benefits - Schedule of Net Benefit Costs (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		$ 0.4	$ 0.5
Interest cost		0.7	0.5
Expected return on plan assets		(1.1)	(0.7)
Amortization of net actuarial losses	[1]	0.3	0.2
Net periodic pension cost		$ 0.3	$ 0.5

[1] Reflects amounts reclassified from accumulated other comprehensive income to net income.