Business, Basis of Presentation and Significant Accounting Policies (Goodwill and Indefinite-Lived Intangible Assets) (Narrative) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018 USD ($) yr	Dec. 31, 2019 USD ($) yr component reportingunit	Dec. 31, 2018 USD ($) yr component reportingunit	Dec. 31, 2017 USD ($) component reportingunit
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Goodwill, carrying amount (in dollars)	$ 1,100,350	$ 1,221,440	$ 1,100,350	$ 1,137,700
Goodwill, pre-tax impairment charge	47,700		47,700
Impairment of Intangible Assets (Excluding Goodwill)		3,300
Pre-Qualifications [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, carrying amount (in dollars)	$ 74,000	$ 72,900	$ 74,000	$ 77,600
Goodwill [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Impairment testing, discount rate sensitivity analysis, spread on discount rate for which evaluation was completed (percentage)		100.00%	100.00%
Terminal Growth Rate [Member] | Minimum [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Goodwill impairment testing, measurement input	0.024	0.030	0.024
Terminal Growth Rate [Member] | Maximum [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Goodwill impairment testing, measurement input	0.035		0.035
Number of Years of Discounted Cash Flows [Member] | Minimum [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Goodwill impairment testing, measurement input | yr	4	5	4
Number of Years of Discounted Cash Flows [Member] | Minimum [Member] | Pre-Qualifications [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, impairment testing, measurement input | yr	2		2
Number of Years of Discounted Cash Flows [Member] | Maximum [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Goodwill impairment testing, measurement input | yr	9	9	9
Number of Years of Discounted Cash Flows [Member] | Maximum [Member] | Pre-Qualifications [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, impairment testing, measurement input | yr	4	4	4
Discount Rate [Member] | Pre-Qualifications [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, impairment testing, measurement input		0.130
Discount Rate [Member] | Minimum [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Goodwill impairment testing, measurement input	0.110	0.130	0.110
Discount Rate [Member] | Minimum [Member] | Pre-Qualifications [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, impairment testing, measurement input	0.130		0.130
Discount Rate [Member] | Maximum [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Goodwill impairment testing, measurement input	0.160	0.160	0.160
Discount Rate [Member] | Maximum [Member] | Pre-Qualifications [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, impairment testing, measurement input	0.140		0.140
Power Generation and Industrial [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Number of aggregated components in reporting unit | component		2	2	2
Goodwill impairment testing, number of reporting units | reportingunit				1
Goodwill, carrying amount (in dollars)	$ 143,100	$ 152,600	$ 143,100	$ 135,800
Goodwill, pre-tax impairment charge			$ 0
Communications [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Number of aggregated components in reporting unit | component		1	1	1
Goodwill impairment testing, number of reporting units | reportingunit		1	2
Goodwill, carrying amount (in dollars)	467,800	$ 541,300	$ 467,800	$ 466,400
Goodwill, pre-tax impairment charge			$ 0
Oil and Gas [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Number of aggregated components in reporting unit | component		1	1	1
Goodwill impairment testing, number of reporting units | reportingunit		3	3	2
Goodwill, carrying amount (in dollars)	339,600	$ 377,600	$ 339,600	$ 385,600
Goodwill, pre-tax impairment charge			47,700
Oil and Gas [Member] | Pre-Qualifications [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, carrying amount (in dollars)	$ 43,000	$ 41,400	$ 43,000
Indefinite-lived intangible assets impairment testing, percentage of estimated fair value in excess of carrying value	16.00%		16.00%
Oil and Gas [Member] | Reporting Unit A, Quantitative Testing [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Goodwill impairment testing, number of reporting units | reportingunit		1
Oil and Gas [Member] | Reporting Unit B, Quantitative Testing [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Goodwill impairment testing, number of reporting units | reportingunit		2
Goodwill, carrying amount (in dollars)	$ 15,000	$ 15,000	$ 15,000
Goodwill impairment testing, reporting unit, percentage of estimated fair value in excess of carrying value	5.00%	15.00%	5.00%
Oil and Gas [Member] | Reporting Unit Or Intangible For Which Impairment Charge Was Recorded [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Goodwill impairment testing, number of reporting units | reportingunit			1
Goodwill, carrying amount (in dollars)	$ 14,000		$ 14,000
Electrical Transmission [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Percentage of aggregated components in reporting unit		100.00%	100.00%	100.00%
Goodwill, carrying amount (in dollars)	$ 149,900	$ 149,900	$ 149,900	$ 149,900
Goodwill, pre-tax impairment charge			$ 0
Other [Member]
Goodwill and Indefinite-Lived Intangible Assets [Line Items]
Number of aggregated components in reporting unit | component		1	1	1