Retirement Benefits - Schedule of Components of Net Periodic Pension Costs (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Net Periodic Pension Cost [Abstract]
Service cost		$ 1.7	$ 1.8	$ 1.6
Interest cost		2.1	2.0	2.0
Expected return on plan assets		(2.4)	(2.6)	(2.3)
Amortization of actuarial losses	[1]	0.4	0.7	0.6
Amortization of transitional obligation		0.0	0.0	(0.1)
Settlement cost		0.0	0.1	0.0
Net periodic pension cost		$ 1.8	$ 2.0	$ 1.8

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