Goodwill and Other Intangible Assets - 2021 Acquisitions - Narrative (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($) yr acquisition	Dec. 31, 2020 USD ($)
Business Acquisition [Line Items]
Goodwill, net	$ 1,338,597	$ 1,243,034
Electrical Transmission
Business Acquisition [Line Items]
Goodwill, net	$ 197,900
2021 Acquisitions
Business Acquisition [Line Items]
Business combinations, number of acquisitions | acquisition	8
Total consideration transferred	$ 644,900
Amortizing intangible assets, weighted average useful life	17 years
Amortizing intangible assets	$ 367,200
Goodwill, net	95,400
Business acquisition, goodwill, expected tax deductible amount	75,000
Estimated fair value of contingent consideration	40,000
Business combination, contingent consideration, current	26,000
Acquisition-related contingent consideration liabilities, range of potential undiscounted earn-out liabilities, low	2,000
Acquisition-related contingent consideration liabilities, range of potential undiscounted earn-out liabilities, high	65,000
2021 Acquisitions | Electrical Transmission
Business Acquisition [Line Items]
Total consideration transferred	452,000
Goodwill, net	$ 48,000
2021 Acquisitions | Minimum | Expected Term
Business Acquisition [Line Items]
Business combinations, contingent consideration, earn-out period (in years) | yr	1
2021 Acquisitions | Maximum | Expected Term
Business Acquisition [Line Items]
Business combinations, contingent consideration, earn-out period (in years) | yr	5
2021 Acquisitions | Customer Relationships
Business Acquisition [Line Items]
Amortizing intangible assets, weighted average useful life	18 years
2021 Acquisitions | Trade Names
Business Acquisition [Line Items]
Amortizing intangible assets, weighted average useful life	17 years
2021 Acquisitions | Customer Relationships And Trade Names
Business Acquisition [Line Items]
Amortizing intangible assets, weighted average useful life	20 years
Amortizing intangible assets	$ 282,000