Acquisitions and Disposals (Details) € in Millions			1 Months Ended	12 Months Ended
	Apr. 26, 2017 USD ($)	Apr. 26, 2017 EUR (€)	Dec. 31, 2018 USD ($) business_unit	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Total cash consideration paid for acquisitions, net of cash acquired				$ 51,800,000	$ 45,700,000	$ 60,500,000
Initial acquisition payments				9,100,000	32,700,000	57,600,000
Total contingent consideration payments for acquisitions				42,700,000
Payments for contingent consideration liability, financing activities				18,600,000	13,000,000	$ 2,900,000
Goodwill acquired during the period				6,100,000	35,000,000
Intangible assets acquired during the period				700,000	13,300,000
Payments in excess of contingent consideration liabilities				24,100,000
Disposed of by Sale | Netherlands Business Unit
Business Acquisition [Line Items]
Number of business units sold | business_unit			1
After tax net gain			$ 3,800,000
7S
Business Acquisition [Line Items]
Payments for contingent consideration liability, financing activities					$ 10,300,000
7S
Business Acquisition [Line Items]
Additional consideration sought from the seller of 7S	$ 23,900,000	€ 20.8
Loss contingency			$ 0	$ 0