| Document and Entity Information | 12 Months Ended |
| Aug. 04, 2015 | |
| Document And Entity Information [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 4, 2015 |
| Trading Symbol | PWR |
| Entity Registrant Name | QUANTA SERVICES INC |
| Entity Central Index Key | 1,050,915 |
| Statements of Operations Recast for Discontinued Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands | 3 Months Ended | 6 Months Ended | 9 Months Ended | 12 Months Ended | |||||||||||
| Mar. 31, 2015 | Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Jun. 30, 2014 | Jun. 30, 2013 | Sep. 30, 2014 | Sep. 30, 2013 | Dec. 31, 2014 | Dec. 31, 2013 | |
| Income Statement [Abstract] | |||||||||||||||
| Revenues | $ 1,861,386 | $ 2,027,614 | $ 2,145,958 | $ 1,838,209 | $ 1,735,448 | $ 1,792,147 | $ 1,618,049 | $ 1,447,263 | $ 1,554,118 | $ 3,573,657 | $ 3,001,381 | $ 5,719,615 | $ 4,619,430 | $ 7,747,229 | $ 6,411,577 |
| Cost of services (including depreciation) | 1,623,480 | 1,715,986 | 1,809,055 | 1,574,000 | 1,479,394 | 1,502,791 | 1,362,172 | 1,223,377 | 1,336,304 | 3,053,394 | 2,559,681 | 4,862,449 | 3,921,853 | 6,578,435 | 5,424,644 |
| Gross profit | 237,906 | 311,628 | 336,903 | 264,209 | 256,054 | 289,356 | 255,877 | 223,886 | 217,814 | 520,263 | 441,700 | 857,166 | 697,577 | 1,168,794 | 986,933 |
| Selling, general and administrative expenses | 145,463 | 204,884 | 196,494 | 135,210 | 168,889 | 139,035 | 120,966 | 115,163 | 109,905 | 304,099 | 225,068 | 500,593 | 346,034 | 705,477 | 485,069 |
| Amortization of intangible assets | 8,293 | 9,097 | 9,125 | 8,202 | 7,833 | 9,697 | 6,613 | 4,667 | 4,888 | 16,035 | 9,555 | 25,160 | 16,168 | 34,257 | 25,865 |
| Operating income | 84,150 | 97,647 | 131,284 | 120,797 | 79,332 | 140,624 | 128,298 | 104,056 | 103,021 | 200,129 | 207,077 | 331,413 | 335,375 | 429,060 | 475,999 |
| Interest expense | (1,400) | (1,334) | (1,321) | (1,128) | (982) | (1,188) | (475) | (503) | (502) | (2,110) | (1,005) | (3,431) | (1,480) | (4,765) | (2,668) |
| Interest income | 453 | 695 | 900 | 599 | 1,542 | 1,150 | 1,139 | 568 | 521 | 2,141 | 1,089 | 3,041 | 2,228 | 3,736 | 3,378 |
| Equity in earnings (losses) of unconsolidated affiliates, including gain on sale of investment | (332) | 112,744 | (332) | (332) | (332) | 112,744 | |||||||||
| Other income (expense), net | (212) | (465) | (378) | (901) | 644 | 558 | (825) | (352) | (514) | (257) | (866) | (635) | (1,691) | (1,100) | (1,133) |
| Income from continuing operations before income taxes | 82,991 | 96,543 | 130,485 | 119,035 | 80,536 | 253,888 | 128,137 | 103,769 | 102,526 | 199,571 | 206,295 | 330,056 | 334,432 | 426,599 | 588,320 |
| Provision for income taxes | 30,601 | 31,738 | 37,195 | 41,220 | 28,854 | 86,967 | 37,724 | 36,796 | 35,388 | 70,074 | 72,184 | 107,269 | 109,908 | 139,007 | 196,875 |
| Net income from continuing operations | 52,390 | 64,805 | 93,290 | 77,815 | 51,682 | 166,921 | 90,413 | 66,973 | 67,138 | 129,497 | 134,111 | 222,787 | 224,524 | 287,592 | 391,445 |
| Net income from discontinued operations | 5,795 | 6,170 | 6,725 | 7,629 | 6,966 | 4,396 | 7,996 | 7,753 | 9,719 | 14,595 | 17,472 | 21,320 | 25,468 | 27,490 | 29,864 |
| Net income | 58,185 | 70,975 | 100,015 | 85,444 | 58,648 | 171,317 | 98,409 | 74,726 | 76,857 | 144,092 | 151,583 | 244,107 | 249,992 | 315,082 | 421,309 |
| Less: Net income attributable to non-controlling interests | 4,701 | 4,399 | 5,367 | 4,362 | 4,240 | 4,620 | 5,503 | 4,489 | 4,776 | 8,602 | 9,265 | 13,969 | 14,768 | 18,368 | 19,388 |
| Net income attributable to common stock | 53,484 | 66,576 | 94,648 | 81,082 | 54,408 | 166,697 | 92,906 | 70,237 | 72,081 | 135,490 | 142,318 | 230,138 | 235,224 | 296,714 | 401,921 |
| Amounts attributable to common stock: | |||||||||||||||
| Net income from continuing operations | 47,689 | 60,406 | 87,923 | 73,453 | 47,442 | 162,301 | 84,910 | 62,484 | 62,362 | 120,895 | 124,846 | 208,818 | 209,756 | 269,224 | 372,057 |
| Net income (loss) from discontinued operations | 5,795 | 6,170 | 6,725 | 7,629 | 6,966 | 4,396 | 7,996 | 7,753 | 9,719 | 14,595 | 17,472 | 21,320 | 25,468 | 27,490 | 29,864 |
| Net income attributable to common stock | $ 53,484 | $ 66,576 | $ 94,648 | $ 81,082 | $ 54,408 | $ 166,697 | $ 92,906 | $ 70,237 | $ 72,081 | $ 135,490 | $ 142,318 | $ 230,138 | $ 235,224 | $ 296,714 | $ 401,921 |
| Earnings (loss) per share attributable to common stock - basic: | |||||||||||||||
| Continuing operations | $ 0.22 | $ 0.27 | $ 0.40 | $ 0.33 | $ 0.22 | $ 0.75 | $ 0.39 | $ 0.30 | $ 0.29 | $ 0.55 | $ 0.59 | $ 0.95 | $ 0.98 | $ 1.22 | $ 1.73 |
| Discontinued operations | 0.03 | 0.03 | 0.03 | 0.04 | 0.03 | 0.02 | 0.04 | 0.03 | 0.05 | 0.07 | 0.08 | 0.10 | 0.12 | 0.13 | 0.14 |
| Net income attributable to common stock | 0.25 | 0.30 | 0.43 | 0.37 | 0.25 | 0.77 | 0.43 | 0.33 | 0.34 | 0.62 | 0.67 | 1.05 | 1.10 | 1.35 | 1.87 |
| Earnings (loss) per share attributable to common stock - diluted | |||||||||||||||
| Continuing operations | 0.22 | 0.27 | 0.40 | 0.33 | 0.22 | 0.75 | 0.39 | 0.30 | 0.29 | 0.55 | 0.59 | 0.95 | 0.98 | 1.22 | 1.73 |
| Discontinued operations | 0.03 | 0.03 | 0.03 | 0.04 | 0.03 | 0.02 | 0.04 | 0.03 | 0.05 | 0.07 | 0.08 | 0.10 | 0.12 | 0.13 | 0.14 |
| Net income attributable to common stock | $ 0.25 | $ 0.30 | $ 0.43 | $ 0.37 | $ 0.25 | $ 0.77 | $ 0.43 | $ 0.33 | $ 0.34 | $ 0.62 | $ 0.67 | $ 1.05 | $ 1.10 | $ 1.35 | $ 1.87 |
| Shares used in computing earnings per share: | |||||||||||||||
| Weighted average basic shares outstanding | 215,473 | 220,451 | 219,492 | 219,612 | 219,033 | 217,287 | 214,866 | 214,314 | 213,453 | 219,345 | 213,833 | 219,395 | 214,178 | 219,668 | 214,929 |
| Weighted average diluted shares outstanding | 215,490 | 220,472 | 219,517 | 219,642 | 219,075 | 217,338 | 214,916 | 214,368 | 213,512 | 219,375 | 213,886 | 219,420 | 214,229 | 219,690 | 214,978 |
| Segment Data Recast for Discontinued Operations | 12 Months Ended |
| Aug. 04, 2015 | |
| Segment Reporting [Abstract] | |
| Segment Data Recast for Discontinued Operations | LOGO Quanta Services, Inc. and Subsidiaries 2015, 2014 and 2013 Segment Data Recast for Discontinued Operations (In thousands) (Unaudited) Three Revenues Electric Power Infrastructure $ 1,240,292 Oil and Gas Infrastructure 621,094 Consolidated revenues $ 1,861,386 Operating income (loss) Electric Power Infrastructure $ 108,992 Oil and Gas Infrastructure 24,147 Corporate and Non-Allocated Costs (48,989 ) Consolidated operating income $ 84,150 Three Three Six Months Three Months Nine Months Three Twelve Revenues Electric Power Infrastructure $ 1,289,591 $ 1,252,842 $ 2,542,433 $ 1,396,157 $ 3,938,590 $ 1,364,081 $ 5,302,671 Oil and Gas Infrastructure 445,857 585,367 1,031,224 749,801 1,781,025 663,533 2,444,558 Consolidated revenues $ 1,735,448 $ 1,838,209 $ 3,573,657 $ 2,145,958 $ 5,719,615 $ 2,027,614 $ 7,747,229 Operating income (loss) Electric Power Infrastructure $ 144,488 $ 112,836 $ 257,324 $ 104,365 $ 361,689 $ 101,296 $ 462,985 Oil and Gas Infrastructure (21,172 ) 55,583 34,411 74,824 109,235 53,562 162,797 Corporate and Non-Allocated Costs (43,984 ) (47,622 ) (91,606 ) (47,905 ) (139,511 ) (57,211 ) (196,722 ) Consolidated operating income $ 79,332 $ 120,797 $ 200,129 $ 131,284 $ 331,413 $ 97,647 $ 429,060 Three Three Six Months Three Months Nine Months Three Twelve Revenues Electric Power Infrastructure $ 1,195,186 $ 1,061,321 $ 2,256,507 $ 1,065,669 $ 3,322,176 $ 1,219,786 $ 4,541,962 Oil and Gas Infrastructure 358,932 385,942 744,874 552,380 1,297,254 572,361 1,869,615 Consolidated revenues $ 1,554,118 $ 1,447,263 $ 3,001,381 $ 1,618,049 $ 4,619,430 $ 1,792,147 $ 6,411,577 Operating income (loss) Electric Power Infrastructure $ 132,483 $ 121,324 $ 253,807 $ 122,973 $ 376,780 $ 146,575 $ 523,355 Oil and Gas Infrastructure 10,357 27,644 38,001 49,873 87,874 50,669 138,543 Corporate and Non-Allocated Costs (39,819 ) (44,912 ) (84,731 ) (44,548 ) (129,279 ) (56,620 ) (185,899 ) Consolidated operating income $ 103,021 $ 104,056 $ 207,077 $ 128,298 $ 335,375 $ 140,624 $ 475,999 |
| Segment Data Recast for Discontinued Operations (Tables) | 12 Months Ended |
| Aug. 04, 2015 | |
| Segment Reporting [Abstract] | |
| Summarized Financial Information | Three Revenues Electric Power Infrastructure $ 1,240,292 Oil and Gas Infrastructure 621,094 Consolidated revenues $ 1,861,386 Operating income (loss) Electric Power Infrastructure $ 108,992 Oil and Gas Infrastructure 24,147 Corporate and Non-Allocated Costs (48,989 ) Consolidated operating income $ 84,150 Three Three Six Months Three Months Nine Months Three Twelve Revenues Electric Power Infrastructure $ 1,289,591 $ 1,252,842 $ 2,542,433 $ 1,396,157 $ 3,938,590 $ 1,364,081 $ 5,302,671 Oil and Gas Infrastructure 445,857 585,367 1,031,224 749,801 1,781,025 663,533 2,444,558 Consolidated revenues $ 1,735,448 $ 1,838,209 $ 3,573,657 $ 2,145,958 $ 5,719,615 $ 2,027,614 $ 7,747,229 Operating income (loss) Electric Power Infrastructure $ 144,488 $ 112,836 $ 257,324 $ 104,365 $ 361,689 $ 101,296 $ 462,985 Oil and Gas Infrastructure (21,172 ) 55,583 34,411 74,824 109,235 53,562 162,797 Corporate and Non-Allocated Costs (43,984 ) (47,622 ) (91,606 ) (47,905 ) (139,511 ) (57,211 ) (196,722 ) Consolidated operating income $ 79,332 $ 120,797 $ 200,129 $ 131,284 $ 331,413 $ 97,647 $ 429,060 Three Three Six Months Three Months Nine Months Three Twelve Revenues Electric Power Infrastructure $ 1,195,186 $ 1,061,321 $ 2,256,507 $ 1,065,669 $ 3,322,176 $ 1,219,786 $ 4,541,962 Oil and Gas Infrastructure 358,932 385,942 744,874 552,380 1,297,254 572,361 1,869,615 Consolidated revenues $ 1,554,118 $ 1,447,263 $ 3,001,381 $ 1,618,049 $ 4,619,430 $ 1,792,147 $ 6,411,577 Operating income (loss) Electric Power Infrastructure $ 132,483 $ 121,324 $ 253,807 $ 122,973 $ 376,780 $ 146,575 $ 523,355 Oil and Gas Infrastructure 10,357 27,644 38,001 49,873 87,874 50,669 138,543 Corporate and Non-Allocated Costs (39,819 ) (44,912 ) (84,731 ) (44,548 ) (129,279 ) (56,620 ) (185,899 ) Consolidated operating income $ 103,021 $ 104,056 $ 207,077 $ 128,298 $ 335,375 $ 140,624 $ 475,999 |
| Segment Data Recast for Discontinued Operations - Summarized Financial Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended | 9 Months Ended | 12 Months Ended | |||||||||||
| Mar. 31, 2015 | Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Jun. 30, 2014 | Jun. 30, 2013 | Sep. 30, 2014 | Sep. 30, 2013 | Dec. 31, 2014 | Dec. 31, 2013 | |
| Segment Reporting Information [Line Items] | |||||||||||||||
| Revenues | $ 1,861,386 | $ 2,027,614 | $ 2,145,958 | $ 1,838,209 | $ 1,735,448 | $ 1,792,147 | $ 1,618,049 | $ 1,447,263 | $ 1,554,118 | $ 3,573,657 | $ 3,001,381 | $ 5,719,615 | $ 4,619,430 | $ 7,747,229 | $ 6,411,577 |
| Operating income (loss) | 84,150 | 97,647 | 131,284 | 120,797 | 79,332 | 140,624 | 128,298 | 104,056 | 103,021 | 200,129 | 207,077 | 331,413 | 335,375 | 429,060 | 475,999 |
| Electric Power Infrastructure [Member] | |||||||||||||||
| Segment Reporting Information [Line Items] | |||||||||||||||
| Revenues | 1,240,292 | 1,364,081 | 1,396,157 | 1,252,842 | 1,289,591 | 1,219,786 | 1,065,669 | 1,061,321 | 1,195,186 | 2,542,433 | 2,256,507 | 3,938,590 | 3,322,176 | 5,302,671 | 4,541,962 |
| Operating income (loss) | 108,992 | 101,296 | 104,365 | 112,836 | 144,488 | 146,575 | 122,973 | 121,324 | 132,483 | 257,324 | 253,807 | 361,689 | 376,780 | 462,985 | 523,355 |
| Oil and Gas Infrastructure Services [Member] | |||||||||||||||
| Segment Reporting Information [Line Items] | |||||||||||||||
| Revenues | 621,094 | 663,533 | 749,801 | 585,367 | 445,857 | 572,361 | 552,380 | 385,942 | 358,932 | 1,031,224 | 744,874 | 1,781,025 | 1,297,254 | 2,444,558 | 1,869,615 |
| Operating income (loss) | 24,147 | 53,562 | 74,824 | 55,583 | (21,172) | 50,669 | 49,873 | 27,644 | 10,357 | 34,411 | 38,001 | 109,235 | 87,874 | 162,797 | 138,543 |
| Corporate and Non-Allocated Costs [Member] | |||||||||||||||
| Segment Reporting Information [Line Items] | |||||||||||||||
| Operating income (loss) | $ (48,989) | $ (57,211) | $ (47,905) | $ (47,622) | $ (43,984) | $ (56,620) | $ (44,548) | $ (44,912) | $ (39,819) | $ (91,606) | $ (84,731) | $ (139,511) | $ (129,279) | $ (196,722) | $ (185,899) |
