Employee Benefits - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Maximum employee contribution matched	100.00%
Number of employees	6
Contribution match	3.00%
Reclassified losses out of AOCI in relation to settlement	$ (0.1)	$ (0.1)	$ (0.3)
Fair value of defined benefit plan assets	223.9	188.2	213.6
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of defined benefit plan assets	17.2
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of defined benefit plan assets	200.0	188.2
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of defined benefit plan assets		6.7
Pension plan | Cost of services and Operating, administrative and other
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan expense	38.8	$ 36.1	$ 27.8
Foreign Plan | UK benefit plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 5.0