Goodwill and Identifiable Intangible Assets, Net - Identifiable Intangible Assets, Net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Identifiable Intangible Assets, Net
Gross Book Value	$ 329,787		$ 329,787		$ 262,456
Accumulated Amortization	(119,623)		(119,623)		(102,482)
Amortization of identifiable intangible assets	10,900	$ 8,100	17,141	$ 13,006
Future amortization expense of identifiable intangible assets
2020 (remainder of the year)	15,557		15,557
2021	24,610		24,610
2022	21,989		21,989
2023	20,535		20,535
2024	19,185		19,185
Thereafter	108,288		108,288
Total	210,164		210,164
Customer Relationships
Identifiable Intangible Assets, Net
Gross Book Value	231,492		231,492		183,061
Accumulated Amortization	(91,882)		$ (91,882)		(80,813)
Customer Relationships | Minimum
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years			1 year
Customer Relationships | Maximum
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years			15 years
Backlog
Identifiable Intangible Assets, Net
Gross Book Value	12,600		$ 12,600		7,400
Accumulated Amortization	(10,822)		$ (10,822)		(6,388)
Backlog | Minimum
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years			1 year
Backlog | Maximum
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years			2 years
Trade Name
Identifiable Intangible Assets, Net
Gross Book Value	85,695		$ 85,695		71,995
Accumulated Amortization	$ (16,919)		$ (16,919)		$ (15,281)
Trade Name | Minimum
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years			2 years
Trade Name | Maximum
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years			25 years