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Equity - Additional Information (Detail) (USD $) | 0 Months Ended | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | ---
Mar. 31, 2013 | Sep. 30, 2014 | Sep. 30, 2013 | Sep. 30, 2014 | Sep. 30, 2013 | Dec. 31, 2013
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 |  |  |  |  |
Shares outstanding |  | 212,462,599 |  | 212,462,599 |  | 212,942,767
Aggregate authorized amount of common stock to be repurchased |  | $ 500,000,000 |  | $ 500,000,000 |  |
Reduction in net income as a result of non controlling interests |  | 5,367,000 | 5,503,000 | 13,969,000 | 14,768,000 |
Carrying value of the investments held by Quanta in variable interest entities |  | 17,600,000 |  | 17,600,000 |  | 7,100,000
Distributions to non-controlling interests |  | 3,000,000 | 2,500,000 | 3,500,000 | 11,800,000 |
Carrying value of the investment held by noncontrolling interest in variable interest entities |  | 17,594,000 |  | 17,594,000 |  | 7,131,000
Treasury Stock [Member] |  |  |  |  |  |
Equity [Line Items] |  |  |  |  |  |
Treasury stock acquired |  | 0 |  | 1,300,000 |  |
Value of treasury stock acquired, cost method |  |  |  | 45,000,000 |  |
Series F Preferred Stock [Member] |  |  |  |  |  |
Equity [Line Items] |  |  |  |  |  |
Number of preferred Stock issued to voting trust |  | 1 |  | 1 |  |
Series G Preferred Stock [Member] |  |  |  |  |  |
Equity [Line Items] |  |  |  |  |  |
Number of preferred Stock issued to voting trust |  | 1 |  | 1 |  |
Exchangeable Shares [Member] |  |  |  |  |  |
Equity [Line Items] |  |  |  |  |  |
Shares outstanding |  | 5,221,377 |  | 5,221,377 |  | 3,500,000
Exchangeable Shares Not Associated With Preferred Stock [Member] |  |  |  |  |  |
Equity [Line Items] |  |  |  |  |  |
Shares outstanding |  | 4,399,858 |  | 4,399,858 |  |
Common Stock Withheld for Settlement of Employee Tax Liabilities [Member] | Treasury Stock [Member] |  |  |  |  |  |
Equity [Line Items] |  |  |  |  |  |
Treasury stock acquired |  |  |  | 300,000 | 400,000 |
Value of treasury stock acquired, cost method |  |  |  | $ 11,900,000 | $ 12,000,000 |

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- Definition Exchangeable shares exchanged for common stock. + References No definition available. + Details
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