Business Combinations - Narratives (Details) - USD ($) $ in Thousands					3 Months Ended	6 Months Ended	12 Months Ended
	Dec. 23, 2020	Nov. 03, 2020	Oct. 13, 2020	Jul. 01, 2019	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Oct. 01, 2020	Sep. 30, 2020
Business Acquisition
Goodwill							$ 865,900	$ 811,400	$ 487,200	$ 817,600	$ 817,600
Gain on bargain purchase							5,000	0	0
Intangible assets amortization expense							$ 45,700	39,800	$ 21,900
Minimum
Business Acquisition
Finite lived intangible asset useful life							2 years
Maximum
Business Acquisition
Finite lived intangible asset useful life							15 years
Sustainable Energy Solutions, Inc.
Business Acquisition
Payments to acquire business	$ 20,000
Potential earn-out not to exceed amount	25,000
Net assets acquired, excluding goodwill	13,400
Goodwill	24,000
Identifiable intangible assets	$ 17,300
BIG
Business Acquisition
Payments to acquire business		$ 20,000
Potential earn-out not to exceed amount		6,000
Net assets acquired, excluding goodwill		8,800
Goodwill		14,800
Identifiable intangible assets		$ 6,800
Alabama Trailers
Business Acquisition
Payments to acquire business			$ 10,000
Gain on bargain purchase			$ 5,000
AXC
Business Acquisition
Payments to acquire business				$ 599,700	$ 592,000
Goodwill						$ 287,900		287,500
Identifiable intangible assets						256,400		256,400
Payment for working capital adjustments					$ 7,700
Net sales								103,100
Operating income								4,600
Intangible assets amortization expense								16,800
Acquisition costs								$ 5,400
Property, plant and equipment						$ 400
AXC | Minimum
Business Acquisition
Finite lived intangible asset useful life				1 year
AXC | Maximum
Business Acquisition
Finite lived intangible asset useful life				14 years