Debt - Narrative (Details) £ in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2017 GBP (£)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Entity's debt and other obligations [Line Items]
Amount outstanding				$ 644.8	$ 508.2
Proceeds from Lines of Credit		$ 1,117.3	$ 768.7
Repayments of Lines of Credit		867.3	984.8
Accounts receivable securitization program
Entity's debt and other obligations [Line Items]
Maximum borrowing capacity				150.0
Amount outstanding				65.6	103.2
Proceeds from the accounts receivable securitization program		443.1	746.8
Payments in respect of accounts receivable securitization program		$ 480.7	$ 658.2
Revolving credit facilities
Entity's debt and other obligations [Line Items]
Maximum borrowing capacity				850.0
Amount outstanding				325.0	75.0
New Line of Credit Facilities
Entity's debt and other obligations [Line Items]
Maximum borrowing capacity				10.0
Amount outstanding				0.0	$ 0.0
U.K. Mortgage
Entity's debt and other obligations [Line Items]
Amount outstanding				$ 29.5
Mortgage principal amount | £	£ 23.0
Fixed interest rate	3.90%			3.90%
Periodic principal payment | £	£ 1.0