Business Combinations - Intangible Assets Acquired (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets, Gross [Abstract]
Aggregate Acquisitions	$ 4.8	$ 12.9
Customer relationships
Finite-Lived Intangible Assets, Gross [Abstract]
Weighted Average Useful Life	7 years	5 years
Estimated Useful Life	7 years
Aggregate Acquisitions	$ 3.9	$ 10.6
Customer relationships | Minimum
Finite-Lived Intangible Assets, Gross [Abstract]
Estimated Useful Life	7 years	5 years
Customer relationships | Maximum
Finite-Lived Intangible Assets, Gross [Abstract]
Estimated Useful Life	7 years	6 years
Customer backlog
Finite-Lived Intangible Assets, Gross [Abstract]
Weighted Average Useful Life	9 months	1 year
Estimated Useful Life	9 months
Aggregate Acquisitions	$ 0.4	$ 1.5
Customer backlog | Minimum
Finite-Lived Intangible Assets, Gross [Abstract]
Estimated Useful Life	9 months	1 year
Customer backlog | Maximum
Finite-Lived Intangible Assets, Gross [Abstract]
Estimated Useful Life	9 months	1 year 6 months
Non-compete agreements
Finite-Lived Intangible Assets, Gross [Abstract]
Weighted Average Useful Life	5 years	5 years
Estimated Useful Life	5 years
Aggregate Acquisitions	$ 0.1	$ 0.3
Non-compete agreements | Minimum
Finite-Lived Intangible Assets, Gross [Abstract]
Estimated Useful Life	5 years	4 years
Non-compete agreements | Maximum
Finite-Lived Intangible Assets, Gross [Abstract]
Estimated Useful Life	5 years	5 years
Trade name
Finite-Lived Intangible Assets, Gross [Abstract]
Weighted Average Useful Life	1 year	1 year
Estimated Useful Life	1 year	1 year
Aggregate Acquisitions	$ 0.1	$ 0.1
Developed software
Finite-Lived Intangible Assets, Gross [Abstract]
Weighted Average Useful Life	3 years	3 years
Estimated Useful Life	3 years	3 years
Aggregate Acquisitions	$ 0.3	$ 0.4