Goodwill and Other Intangible Assets (2021 Acquisitions) (Narrative) (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($) acquisition	Dec. 31, 2020 USD ($) yr acquisition
Business Acquisition [Line Items]
Business combinations, number of acquisitions | acquisition		5
Goodwill, net	$ 1,331,699	$ 1,243,034
Electrical Transmission
Business Acquisition [Line Items]
Business combinations, number of acquisitions | acquisition		1
Goodwill, net	$ 196,400
2021 Acquisitions
Business Acquisition [Line Items]
Business combinations, number of acquisitions | acquisition	7
Total consideration transferred	$ 629,100
Amortizing intangible assets, weighted average useful life	17 years
Amortizing intangible assets	$ 367,200
Goodwill, net	88,100
Business acquisition, goodwill, expected tax deductible amount	74,000
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, high	86,000
2021 Acquisitions | Electrical Transmission
Business Acquisition [Line Items]
Total consideration transferred	450,000
Goodwill, net	$ 46,000
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