Goodwill and Other Intangible Assets Goodwill and Other Intangible Assets (2019 Acquisitions) (Narrative) (Details) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) yr acquisition	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) acquisition
Business Combinations [Line Items]
Business combinations, number of acquisitions | acquisition	6		3
Amounts due to former owners, subsequently paid	$ 8,458	$ 0	$ 6,301
Business combinations, contingent consideration liabilities, range of potential undiscounted earn-out liabilities, low	54,000
Business combinations, contingent consideration liabilities, range of potential undiscounted earn-out liabilities, high	$ 274,000
2019 Acquisitions [Member]
Business Combinations [Line Items]
Business combinations, percentage of interests acquired	96.00%
Business combinations, acquired finite-lived intangible assets, weighted average lives (in years)	11 years
Business combinations, goodwill, expected tax deductible amount	$ 12,000
Business combinations, contingent consideration, earn-out liabilities	22,200
Business combinations, contingent consideration, mandatorily redeemable non-controlling interest	16,700
Business combinations, contingent consideration liabilities, range of potential undiscounted earn-out liabilities, low	2,000
Business combinations, contingent consideration liabilities, range of potential undiscounted earn-out liabilities, high	$ 82,000
2019 Acquisitions [Member] | Customer Relationships [Member]
Business Combinations [Line Items]
Business combinations, acquired finite-lived intangible assets, weighted average lives (in years)	11 years
2019 Acquisitions [Member] | Backlog [Member]
Business Combinations [Line Items]
Business combinations, acquired finite-lived intangible assets, weighted average lives (in years)	2 years
2019 Acquisitions [Member] | Other Amortizing Intangible Assets [Member]
Business Combinations [Line Items]
Business combinations, acquired finite-lived intangible assets, weighted average lives (in years)	5 years
2019 Acquisitions [Member] | Expected Term [Member]
Business Combinations [Line Items]
Business combinations, contingent consideration, earn-out period (in years) | yr	5
Oil and Gas [Member]
Business Combinations [Line Items]
Business combinations, number of acquisitions | acquisition	1
Communications [Member]
Business Combinations [Line Items]
Business combinations, number of acquisitions | acquisition	4
Power Generation and Industrial [Member]
Business Combinations [Line Items]
Business combinations, number of acquisitions | acquisition	1
Management [Member] | 2019 Acquisitions [Member]
Business Combinations [Line Items]
Business combination, liabilities assumed, amounts due to former owners	$ 11,000
Amounts due to former owners, subsequently paid	$ 2,000