Employee Benefit Plans - Summary of Plan Information Relating to Participation in Multi-Employer Pension Plans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Multiemployer Plans [Line Items]
Contributions	$ 55,054	$ 63,572	$ 45,202
National Electrical Benefit Fund [Member]
Multiemployer Plans [Line Items]
Employer Identification Number	53-0181657-001
PPA Zone Status	Green	Green
Subject to Financial Improvement/ Rehabilitation Plan	No
Contributions	17,268	18,509	9,704
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	Varies through May 2017
Laborers National Pension Fund [Member]
Multiemployer Plans [Line Items]
Employer Identification Number	75-1280827-001
PPA Zone Status	Green	Green
Subject to Financial Improvement/ Rehabilitation Plan	No
Contributions	4,681	1,906	1,903
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	May 2014
Pipeline Industry Pension Fund [Member]
Multiemployer Plans [Line Items]
Employer Identification Number	73-6146433-001
PPA Zone Status	Green	Green
Subject to Financial Improvement/ Rehabilitation Plan	No
Contributions	4,511	7,434	101
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	Varies through May 2014
Plan years in which Quanta contributions were five percent or more of total plan contributions	2012
Central Pension Fund of the IUOE & Participating Employers [Member]
Multiemployer Plans [Line Items]
Employer Identification Number	36-6052390-001
PPA Zone Status	Green	Green
Subject to Financial Improvement/ Rehabilitation Plan	No
Contributions	4,259	6,843	4,439
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	May 2014
Eighth District Electrical Pension Fund [Member]
Multiemployer Plans [Line Items]
Employer Identification Number	84-6100393-001
PPA Zone Status	Green	Green
Subject to Financial Improvement/ Rehabilitation Plan	No
Contributions	1,790	4,415	3,533
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	Varies through August 2016
Eighth District Electrical Pension Fund [Member] \| Maximum [Member]
Multiemployer Plans [Line Items]
Plan years in which Quanta contributions were five percent or more of total plan contributions	2012
Eighth District Electrical Pension Fund [Member] \| Minimum [Member]
Multiemployer Plans [Line Items]
Plan years in which Quanta contributions were five percent or more of total plan contributions	2011
Operating Engineers Local Three Two Four Pension Fund [Member]
Multiemployer Plans [Line Items]
Employer Identification Number	38-1900637-001
PPA Zone Status	Red	Red
Subject to Financial Improvement/ Rehabilitation Plan	Implemented
Contributions	818	135
Surcharge Imposed	Yes
Expiration Date of Collective Bargaining Agreement	Varies through April 2018
Joint Pension Local Union 164 IBEW [Member]
Multiemployer Plans [Line Items]
Employer Identification Number	22-6031199-001
PPA Zone Status	Yellow	Yellow
Subject to Financial Improvement/ Rehabilitation Plan	Implemented
Contributions	222	515	2,887
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	May 2014
Plan years in which Quanta contributions were five percent or more of total plan contributions	2011
NECA-IBEW Pension Trust [Member]
Multiemployer Plans [Line Items]
Employer Identification Number	51-6029903-001
PPA Zone Status	Green	Green
Subject to Financial Improvement/ Rehabilitation Plan	No
Contributions	7	19	6,707
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	May 2014
Plan years in which Quanta contributions were five percent or more of total plan contributions	2011
IBEW Local 246 Pension Plan [Member]
Multiemployer Plans [Line Items]
Employer Identification Number	34-6582842-001
PPA Zone Status	Yellow	Yellow
Subject to Financial Improvement/ Rehabilitation Plan	No
Contributions		130	1,977
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	October 2012
IBEW Local 246 Pension Plan [Member] \| Maximum [Member]
Multiemployer Plans [Line Items]
Plan years in which Quanta contributions were five percent or more of total plan contributions	2012
IBEW Local 246 Pension Plan [Member] \| Minimum [Member]
Multiemployer Plans [Line Items]
Plan years in which Quanta contributions were five percent or more of total plan contributions	2011
Central States, Southeast, and Southwest Areas Pension Plan [Member]
Multiemployer Plans [Line Items]
Employer Identification Number	36-6044243-001
PPA Zone Status	Red	Red
Subject to Financial Improvement/ Rehabilitation Plan	Implemented
Contributions		22	540
Surcharge Imposed	Yes
All Other Plans [Member]
Multiemployer Plans [Line Items]
Contributions	$ 21,498	$ 23,644	$ 13,411

Multiemployer Plans Number

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- Definition

Significant Periods Of Multiemployer Contributions Exceeding Specified Percentage

+ References

No definition available.

+ Details

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- Definition

Amount of contributions made to multiemployer plans by the employer. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450702-114947

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 9

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450691-114947

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 5

-Subparagraph (e)(1)

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450657-114947

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- Definition

Indicate the multiemployer plan's certified zone status as currently required by the Pension Protection Act of 2006 or a subsequent amendment thereof. The zone status categories are red (critical status), orange (seriously endangered), yellow (endangered), and green (none of the above). The acceptable values are "red", "orange", "yellow", "green", "other", and "NA". A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 5

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450657-114947

+ Details

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Period Type:	duration

- Definition

Description of the significant collective-bargaining arrangements within the range of expiration dates for collective-bargaining arrangements requiring contributions to a multiemployer plan as well as other information to help investors understand the significance of the collective-bargaining agreements and when they expire. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 5

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450657-114947

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- Definition

Indicate whether a funding improvement plan or rehabilitation plan has been implemented or is pending for a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers. The acceptable values are "no", "pending", "implemented", "other", and "NA".

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 5

-Subparagraph (f)(1)

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450657-114947

+ Details

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- Definition

Indicate whether the employer paid a surcharge to the pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers. The acceptable values are "no", "yes", and "NA".

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 5

-Subparagraph (f)(2)

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450657-114947

+ Details

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Balance Type:	na
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