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Equity - Additional Information (Detail) (USD $) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2013 | Mar. 31, 2013 | Jun. 30, 2012 | Jun. 30, 2013 | Jun. 30, 2012 | Dec. 31, 2012
Stockholders Equity [Line Items] |  |  |  |  |  |
Minimum number of shares that can be exchanged by exchangeable shareholders unless the number of remaining exchangeable shares registered in the name of the holder is less |  |  |  | 50,000 |  |
Number of shares of Common stock received for each exchangeable share |  |  |  | 1 |  |
Exchangeable shares exchanged for common stock |  | 409,110 |  |  |  |
Reduction in net income as a result of non controlling interests | $ 4,489,000 |  | $ 4,259,000 | $ 9,265,000 | $ 8,546,000 |
Carrying value of the investments held by Quanta in variable interest entities | 5,300,000 |  |  | 5,300,000 |  | 5,400,000
Distributions to noncontrolling interests | 3,900,000 |  | 3,700,000 | 9,300,000 | 6,200,000 |
Carrying value of the investment held by noncontrolling interest in variable interest entities | 5,321,000 |  |  | 5,321,000 |  | 5,368,000
Common Stock Withheld for Settlement of Employee Tax Liabilities [Member] |  |  |  |  |  |
Stockholders Equity [Line Items] |  |  |  |  |  |
Treasury stock acquired |  |  |  | 372,015 | 286,954 |
Value of treasury stock acquired, cost method |  |  |  | $ 11,900,000 | $ 6,100,000 |
Series F Preferred Stock [Member] |  |  |  |  |  |
Stockholders Equity [Line Items] |  |  |  |  |  |
Number of preferred Stock issued to voting trust | 1 |  |  | 1 |  |

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- Definition Minimum number of shares that can be exchanged by exchangeable shareholders unless number of remaining exchangeable shares registered in name of holder is less. + References No definition available. + Details
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- Definition Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (that is, noncontrolling interest, previously referred to as minority interest). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.31) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 27 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 20 -Article 7 + Details
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