Goodwill and Identifiable Assets Goodwill (Details) - USD ($) $ in Millions			12 Months Ended
	Oct. 17, 2019	Jan. 25, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Amortization of intangible assets			$ 51.1	$ 58.5	$ 33.4
Goodwill [Roll Forward]
Gross goodwill, period start			1,421.1	894.1
Goodwill, Acquired During Period				528.2
Translation adjustment			(0.3)	(1.2)
Gross goodwill, period end			1,486.9	1,421.1	894.1
Apex
Goodwill [Line Items]
Amortization of intangible assets			20.3	26.2	29.4
Goodwill [Roll Forward]
Gross goodwill, period start			(662.1)	662.1
Translation adjustment			0.0
Gross goodwill, period end			(703.5)	(662.1)	662.1
Oxford
Goodwill [Line Items]
Amortization of intangible assets			3.7	4.2	4.0
Goodwill [Roll Forward]
Gross goodwill, period start			(230.8)	232.0
Translation adjustment			(0.3)	(1.2)
Gross goodwill, period end			(230.5)	(230.8)	232.0
ECS
Goodwill [Line Items]
Amortization of intangible assets			27.1	28.1	0.0
Goodwill [Roll Forward]
Gross goodwill, period start			528.2	0.0
Gross goodwill, period end			552.9	528.2	$ 0.0
DHA
Goodwill [Roll Forward]
Goodwill, Acquired During Period		$ 24.7	24.7
DHA | ECS
Goodwill [Roll Forward]
Goodwill, Acquired During Period			24.7
Intersys
Goodwill [Roll Forward]
Goodwill, Acquired During Period	$ 41.4		41.4
Intersys | Apex
Goodwill [Roll Forward]
Goodwill, Acquired During Period			$ 41.4
ECS
Goodwill [Roll Forward]
Goodwill, Acquired During Period				$ 528.2