Revenue from Contracts with Customers - Schedule of Revenue, Remaining Performance Obligation (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Schedule of Remaining Performance Obligations [Line Items]
Remaining performance obligations	$ 3,964,282
Remaining performance obligations, percent	100.00%
UNITED STATES
Schedule of Remaining Performance Obligations [Line Items]
Remaining performance obligations	$ 3,833,758
Remaining performance obligations, percent	97.00%
UNITED STATES \| United States Electrical Construction And Facilities Services
Schedule of Remaining Performance Obligations [Line Items]
Remaining performance obligations	$ 1,085,571
Remaining performance obligations, percent	27.00%
UNITED STATES \| United States Mechanical Construction And Facilities Services
Schedule of Remaining Performance Obligations [Line Items]
Remaining performance obligations	$ 2,245,584
Remaining performance obligations, percent	57.00%
UNITED STATES \| United States Building Services
Schedule of Remaining Performance Obligations [Line Items]
Remaining performance obligations	$ 435,074
Remaining performance obligations, percent	11.00%
UNITED STATES \| United States Industrial Services
Schedule of Remaining Performance Obligations [Line Items]
Remaining performance obligations	$ 67,529
Remaining performance obligations, percent	2.00%
UNITED KINGDOM \| United Kingdom Building Services
Schedule of Remaining Performance Obligations [Line Items]
Remaining performance obligations	$ 130,524
Remaining performance obligations, percent	3.00%

[Line Items] for Schedule of Remaining Performance Obligations [Table]

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- Definition

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130556-203045

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- Definition

Percentage of remaining performance obligation to total remaining performance obligation not recognized as revenue.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130556-203045

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