Revenue - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 01, 2018	Apr. 02, 2017	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Earnings invested in the business	$ 1,153.2			$ 983.6
Revenue	$ 1,369.9	$ 1,289.7
Customer payment terms	60 days
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Earnings invested in the business			$ 3.4
Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Customer contracts			5.2
Deferred tax liability			1.2
Transferred at Point in Time | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue			0.6
Americas
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 1,068.0	1,044.5
Americas | Global Talent Solutions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	468.6	475.7
EMEA
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	296.8	241.0
EMEA | Global Talent Solutions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	12.1	$ 7.4
Deferred Sales Commissions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Capitalized contract cost	2.8		3.2
Capitalized contract cost, amortization expense	0.4
Deferred Fulfillment Costs
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Capitalized contract cost	1.6		$ 2.0
Capitalized contract cost, amortization expense	$ 2.1