Business Combinations (Narrative) (Details)				3 Months Ended		9 Months Ended		12 Months Ended
	May 04, 2020 USD ($)	Aug. 23, 2019 USD ($)	Jan. 01, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) company	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) company	Dec. 31, 2018 USD ($)
Business Acquisition [Line Items]
Number of businesses acquired | company						1		3
Contingent liability				$ 3,352,000		$ 3,352,000		$ 10,095,000	$ 24,976,000
Reduction of acquisition earn-out contingent liability				(0.0)	$ (0.0)	3,300,000	$ 17,100,000
Change in foreign currency exchange rate				5,900,000		15,900,000
Contingent Accrued Earn-out Acquisition Consideration
Business Acquisition [Line Items]
Contingent liability				3,400,000		3,400,000		10,100,000
Business combination, contingent long term liability				0		0		1,500,000
Contingent liability for accrued earn-out acquisition consideration				3,400,000		3,400,000		$ 8,600,000
Zillious
Business Acquisition [Line Items]
Ownership percentage			80.00%
Trimax
Business Acquisition [Line Items]
Payments to acquire businesses	$ 9,900,000
Wallstreet Canada
Business Acquisition [Line Items]
Payments to acquire businesses		$ 2,100,000
Essel
Business Acquisition [Line Items]
Payments to acquire businesses			$ 8,700,000
Essel | Maximum
Business Acquisition [Line Items]
Contingent liability			721,000
Zillious
Business Acquisition [Line Items]
Payments to acquire businesses			10,100,000
Contingent liability				$ 0		$ 0
Zillious | Maximum
Business Acquisition [Line Items]
Contingent liability			$ 2,200,000