Quanta Services (PWR) 10-K 28 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Feb. 21, 2018	Jun. 30, 2017
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	PWR
Entity Registrant Name	QUANTA SERVICES INC
Entity Central Index Key	1,050,915
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 4.9
Common Stock Class Undefined
Document Information [Line Items]
Entity Common Stock Shares, Outstanding		153,744,728
Series G Preferred Stock
Document Information [Line Items]
Entity Common Stock Shares, Outstanding		1
Exchangeable Shares Associated with Series G Preferred Stock
Document Information [Line Items]
Entity Common Stock Shares, Outstanding		449,929
Exchangeable Shares Not Associated with Preferred Stock
Document Information [Line Items]
Entity Common Stock Shares, Outstanding		36,183

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Cash and cash equivalents	$ 138,285	$ 112,183
Accounts receivable, net of allowances of $4,465 and $2,752	1,985,077	1,500,115
Costs and estimated earnings in excess of billings on uncompleted contracts	497,292	473,308
Inventories	80,890	88,548
Prepaid expenses and other current assets	168,363	114,591
Total current assets	2,869,907	2,288,745
Property and equipment, net of accumulated depreciation of $981,275 and $862,825	1,288,602	1,174,094
Other assets, net	189,866	101,028
Other intangible assets, net of accumulated amortization of $335,507 and $297,313	263,179	187,023
Goodwill	1,868,600	1,603,169
Total assets	6,480,154	5,354,059
Current Liabilities:
Current maturities of long-term debt and short-term debt	1,220	7,563
Accounts payable and accrued expenses	1,057,460	922,819
Billings in excess of costs and estimated earnings on uncompleted contracts	433,387	274,846
Total current liabilities	1,492,067	1,205,228
Long-term debt and notes payable, net of current maturities	670,721	353,562
Deferred income taxes	179,381	192,834
Insurance and other non-current liabilities	342,356	259,733
Total liabilities	2,684,525	2,011,357
Commitments and Contingencies
Equity:
Common stock, value	2	1
Additional paid-in capital	1,889,356	1,749,306
Retained earnings	2,191,059	1,876,081
Accumulated other comprehensive loss	(203,395)	(271,673)
Treasury stock, 1,876,828 and 0 common shares	(85,451)	(14,288)
Total stockholders’ equity	3,791,571	3,339,427
Non-controlling interests	4,058	3,275
Total equity	3,795,629	3,342,702
Total liabilities and equity	6,480,154	5,354,059
Exchangeable Shares
Equity:
Common stock, value	0	0
Series F Preferred Stock
Equity:
Preferred stock, value	0	0
Series G Preferred Stock
Equity:
Preferred stock, value	$ 0	$ 0

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Allowances on accounts receivable, current	$ 4,465	$ 2,752
Accumulated depreciation on property and equipment	981,275	862,825
Accumulated amortization on other intangible assets	$ 335,507	$ 297,313
Common stock, par value (in usd per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)	600,000,000	600,000,000
Common stock, shares issued (in shares)	155,219,154	144,710,773
Common stock, shares outstanding (in shares)	153,342,326	144,710,773
Treasury stock, common shares (in shares)	1,876,828	0
Exchangeable Shares
Common stock, shares issued (in shares)	486,112	6,515,453
Common stock, shares outstanding (in shares)	486,112	6,515,453
Exchangeable shares, par value (in usd per share)
Series F Preferred Stock
Preferred stock, par value (in usd per share)	$ 0.00001	$ 0.00001
Preferred stock, shares authorized (in shares)	0	1
Preferred stock, shares issued (in shares)	0	1
Preferred stock, shares outstanding (in shares)	0	1
Series G Preferred Stock
Preferred stock, par value (in usd per share)	$ 0.00001	$ 0.00001
Preferred stock, shares authorized (in shares)	1	1
Preferred stock, shares issued (in shares)	1	1
Preferred stock, shares outstanding (in shares)	1	1

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenues	$ 9,466,478,000	$ 7,651,319,000	$ 7,572,436,000
Cost of services (including depreciation)	8,224,618,000	6,637,519,000	6,648,771,000
Gross profit	1,241,860,000	1,013,800,000	923,665,000
Selling, general and administrative expenses	777,920,000	653,338,000	592,863,000
Amortization of intangible assets	32,205,000	31,685,000	34,848,000
Asset impairment charges	58,057,000	7,964,000	58,451,000
Change in fair value of contingent consideration liabilities	(5,171,000)	0	0
Operating income	378,849,000	320,813,000	237,503,000
Interest expense	(20,946,000)	(14,887,000)	(8,024,000)
Interest income	832,000	2,423,000	1,493,000
Other income (expense), net	(4,978,000)	(663,000)	(2,297,000)
Income from continuing operations before income taxes	353,757,000	307,686,000	228,675,000
Provision for income taxes	35,532,000	107,246,000	97,472,000
Net income from continuing operations	318,225,000	200,440,000	131,203,000
Net income (loss) from discontinued operations	0	(342,000)	190,621,000
Net income	318,225,000	200,098,000	321,824,000
Less: Net income attributable to non-controlling interests	3,247,000	1,715,000	10,917,000
Net income attributable to common stock	314,978,000	198,383,000	310,907,000
Amounts attributable to common stock:
Net income from continuing operations	314,978,000	198,725,000	120,286,000
Net income (loss) from discontinued operations	0	(342,000)	190,621,000
Net income attributable to common stock	$ 314,978,000	$ 198,383,000	$ 310,907,000
Basic earnings per share attributable to common stock:
Continuing operations (in usd per share)	$ 2.02	$ 1.26	$ 0.62
Discontinued operations (in usd per share)	0	0	0.97
Net income attributable to common stock (in usd per share)	$ 2.02	$ 1.26	$ 1.59
Weighted average basic shares outstanding (in shares)	156,124	157,287	195,113
Diluted earnings per share attributable to common stock:
Continuing operations (in usd per share)	$ 2	$ 1.26	$ 0.62
Discontinued operations (in usd per share)	0	0	0.97
Net income attributable to common stock (in usd per share)	$ 2	$ 1.26	$ 1.59
Weighted average diluted shares outstanding (in shares)	157,155	157,288	195,120

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 318,225	$ 200,098	$ 321,824
Other comprehensive income (loss), net of tax provision:
Foreign currency translation adjustment, net of tax of $0, $0 and $0	67,404	23,137	(171,458)
Other, net of tax of $(347), $46 and $(28)	874	(121)	59
Other comprehensive income (loss)	68,278	23,016	(171,399)
Comprehensive income	386,503	223,114	150,425
Less: Comprehensive income attributable to non-controlling interests	3,247	1,715	10,917
Total comprehensive income attributable to Quanta stockholders	$ 383,256	$ 221,399	$ 139,508

Consolidated Statements of Com6

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Foreign currency translation adjustment, tax	$ 0	$ 0	$ 0
Other comprehensive income (loss) other, tax	$ (347)	$ 46	$ (28)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows from Operating Activities of Continuing Operations:
Net income	$ 318,225,000	$ 200,098,000	$ 321,824,000
Adjustments to reconcile net income to net cash provided by operating activities of continuing operations —
(Income) loss from discontinued operations	0	342,000	(190,621,000)
Depreciation	183,808,000	170,240,000	162,845,000
Amortization of intangible assets	32,205,000	31,685,000	34,848,000
Asset impairment charges	58,057,000	7,964,000	58,451,000
Change in fair value of contingent consideration liabilities	(5,171,000)	0	0
Equity in losses of unconsolidated affiliates	10,945,000	979,000	466,000
Amortization of debt issuance costs	1,321,000	1,356,000	1,251,000
Gain on sale of property and equipment	(549,000)	(734,000)	(2,773,000)
Foreign currency loss	409,000	880,000	2,490,000
Provision for (recovery of) doubtful accounts	87,000	(543,000)	224,000
Deferred income tax benefit	(32,130,000)	(15,695,000)	(19,403,000)
Non-cash stock-based compensation	46,448,000	42,843,000	36,939,000
Changes in operating assets and liabilities, net of non-cash transactions	(241,180,000)	(49,228,000)	222,108,000
Net cash provided by operating activities of continuing operations	372,475,000	390,187,000	628,649,000
Cash Flows from Investing Activities of Continuing Operations:
Proceeds from sale of property and equipment	23,348,000	21,975,000	26,178,000
Additions of property and equipment	(244,651,000)	(212,555,000)	(209,968,000)
Cash paid for acquisitions, net of cash acquired	(361,217,000)	(68,788,000)	(112,914,000)
Investments in and return of equity from unconsolidated affiliates	8,986,000	(10,309,000)	(6,074,000)
Cash received from (paid for) other investments, net	275,000	4,752,000	(4,338,000)
Cash withdrawn from (deposited to) restricted cash	(2,566,000)	(1,119,000)	214,000
Cash paid for intangible assets	0	0	(211,000)
Net cash used in investing activities of continuing operations	(575,825,000)	(266,044,000)	(307,113,000)
Cash Flows from Financing Activities of Continuing Operations:
Borrowings under credit facility	2,932,338,000	2,744,453,000	3,349,385,000
Payments under credit facility	(2,624,404,000)	(2,860,673,000)	(2,935,752,000)
Payments on other long-term debt	(5,361,000)	(6,959,000)	(2,683,000)
Borrowings of short-term debt	0	2,754,000	4,872,000
Payments on short-term debt	(2,783,000)	(4,711,000)	(5,170,000)
Debt issuance and amendment costs	(1,507,000)	0	(3,795,000)
Distributions to non-controlling interests, net of contributions received	(2,001,000)	(761,000)	(18,915,000)
Payments related to tax withholding for share-based compensation	(18,543,000)	(8,340,000)	(9,797,000)
Exercise of stock options	25,000	401,000	372,000
Repurchase of common stock, including accelerated stock repurchases	(50,000,000)	0	(1,606,361,000)
Net cash provided by (used in) financing activities of continuing operations	227,764,000	(133,836,000)	(1,227,844,000)
Discontinued operations:
Net cash provided by (used in) operating activities	0	(1,035,000)	22,342,000
Net cash provided by (used in) investing activities	0	(6,080,000)	825,376,000
Net cash provided by (used in) discontinued operations	0	(7,115,000)	847,718,000
Effect of foreign exchange rate changes on cash and cash equivalents	1,688,000	220,000	(3,154,000)
Net increase (decrease) in cash and cash equivalents	26,102,000	(16,588,000)	(61,744,000)
Cash and cash equivalents, beginning of year	112,183,000	128,771,000	190,515,000
Cash and cash equivalents, end of year	$ 138,285,000	$ 112,183,000	$ 128,771,000

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Exchangeable Shares	Series F Preferred Stock	Series G Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Total Stockholders' Equity	Non-controlling Interests
Balance at Dec. 31, 2014	$ 4,525,540				$ 2	$ 3,592,906	$ 1,366,791	$ (123,290)	$ (321,936)	$ 4,514,473	$ 11,067
Balance (in shares) at Dec. 31, 2014		7,325,971	1	1	210,819,790
Other comprehensive income (loss)	(171,399)							(171,399)		(171,399)
Acquisitions	9,379					10,127				10,127	(748)
Acquisitions (in shares)					461,037
Restricted stock and restricted stock unit activity	26,941					37,309			(10,368)	26,941
Restricted stock and restricted stock unit activity (in shares)					395,427
Stock options exercised	431					431				431
Stock options exercised (in shares)					32,390
Exchange of exchangeable shares (in shares)		(449,929)			449,929
Income tax impact from long-term incentive plans	375					375				375
Common stock repurchases	(1,456,361)								(1,456,361)	(1,456,361)
Common stock/Settlement of accelerated stock repurchases (in shares)					(59,251,407)
Accelerated stock repurchases not yet settled	(150,000)					(150,000)				(150,000)
Vests in deferred compensation plan	0					6,592			(6,592)
Distributions to non-controlling interests, net of contributions received	(18,915)										(18,915)
Net income	321,824						310,907			310,907	10,917
Balance at Dec. 31, 2015	3,087,815				$ 2	3,497,740	1,677,698	(294,689)	(1,795,257)	3,085,494	2,321
Balance (in shares) at Dec. 31, 2015		6,876,042	1	1	152,907,166
Other comprehensive income (loss)	23,016							23,016		23,016
Acquisitions	1,508					1,508				1,508
Acquisitions (in shares)					70,840
Restricted stock and restricted stock unit activity	34,505					42,843			(8,338)	34,505
Restricted stock and restricted stock unit activity (in shares)					760,395
Stock options exercised	425					425				425
Stock options exercised (in shares)					25,423
Exchange of exchangeable shares (in shares)		(360,589)			360,589
Income tax impact from long-term incentive plans	(3,904)					(3,904)				(3,904)
Common stock/Settlement of accelerated stock repurchases (in shares)					(9,413,640)
Settlement of accelerated stock repurchases	0					150,000			(150,000)
Vests in deferred compensation plan	0					6,822			(6,822)
Retirement of treasury stock	0				$ (1)	(1,946,128)			1,946,129
Distributions to non-controlling interests	(761)										(761)
Net income	200,098						198,383			198,383	1,715
Balance at Dec. 31, 2016	3,342,702				$ 1	1,749,306	1,876,081	(271,673)	(14,288)	3,339,427	3,275
Balance (in shares) at Dec. 31, 2016		6,515,453	1	1	144,710,773
Other comprehensive income (loss)	68,278							68,278		68,278
Acquisitions	89,604					89,604				89,604
Acquisitions (in shares)					2,982,346
Restricted stock and restricted stock unit activity	29,259				$ 1	47,825			(18,567)	29,259
Restricted stock and restricted stock unit activity (in shares)					1,000,935
Stock options exercised	25					25				25
Stock options exercised (in shares)					1,223
Exchange of exchangeable shares (in shares)		(6,029,341)			6,029,341
Common stock repurchases	(50,000)								(50,000)	(50,000)
Common stock/Settlement of accelerated stock repurchases (in shares)					(1,382,292)
Vests in deferred compensation plan	0					2,596			(2,596)
Retirement of preferred stock (in shares)			(1)
Distributions to non-controlling interests	(2,001)										(2,001)
Buyout of a non-controlling interest	(463)										(463)
Net income	318,225						314,978			314,978	3,247
Balance at Dec. 31, 2017	$ 3,795,629				$ 2	$ 1,889,356	$ 2,191,059	$ (203,395)	$ (85,451)	$ 3,791,571	$ 4,058
Balance (in shares) at Dec. 31, 2017		486,112	0	1	153,342,326

Business and Organization

Business and Organization	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Organization	BUSINESS AND ORGANIZATION: Quanta Services, Inc. (Quanta) is a leading provider of specialty contracting services, offering infrastructure solutions primarily to the electric power, oil and gas and communication industries in the United States, Canada, Australia, Latin America and select other international markets. Quanta reports its results under two reportable segments: (1) Electric Power Infrastructure Services and (2) Oil and Gas Infrastructure Services. Electric Power Infrastructure Services Segment The Electric Power Infrastructure Services segment provides comprehensive network solutions to customers in the electric power industry. Services performed by the Electric Power Infrastructure Services segment generally include the design, installation, upgrade, repair and maintenance of electric power transmission and distribution infrastructure and substation facilities along with other engineering and technical services. This segment also provides emergency restoration services, including the repair of infrastructure damaged by inclement weather, the energized installation, maintenance and upgrade of electric power infrastructure utilizing unique bare hand and hot stick methods and Quanta’s proprietary robotic arm technologies, and the installation of “smart grid” technologies on electric power networks. In addition, this segment designs, installs and maintains renewable energy generation facilities, consisting of solar, wind and certain types of natural gas generation facilities, and related switchyards and transmission infrastructure. To a lesser extent, the segment also provides comprehensive communications infrastructure services to wireline, fiber and wireless carrier customers within the communications industry; services in connection with the construction of electric power generation facilities; the design, installation, maintenance and repair of commercial and industrial wiring; and the installation of traffic networks and cable and control systems for light rail lines. Oil and Gas Infrastructure Services Segment The Oil and Gas Infrastructure Services segment provides comprehensive network solutions to customers involved in the development, transportation, storage and processing of natural gas, oil and other pipeline products. Services performed by the Oil and Gas Infrastructure Services segment generally include the design, installation, repair and maintenance of pipeline transmission and distribution systems, gathering systems, production systems, storage systems and compressor and pump stations, as well as related trenching, directional boring and mechanized welding services. In addition, this segment’s services include pipeline protection, integrity testing, rehabilitation and replacement, and fabrication of pipeline support systems and related structures and facilities. Quanta also serves the offshore and inland water energy markets, primarily providing services to oil and gas exploration platforms, including mechanical installation (or “hook-ups”), electrical and instrumentation, pre-commissioning and commissioning, coatings, shallow water pipeline installation, fabrication and marine asset repair. To a lesser extent, this segment designs, installs and maintains fueling systems, as well as water and sewer infrastructure. Through a recent acquisition discussed below, Quanta expanded its service offerings in this segment to include high-pressure and critical-path turnaround services to the downstream and midstream energy markets and enhanced its capabilities with respect to instrumentation and electrical services, piping, fabrication and storage tank services. Acquisitions On July 20, 2017, Quanta acquired Stronghold, Ltd. and Stronghold Specialty, Ltd. (collectively Stronghold), a specialized services business located in the United States that provides high-pressure and critical-path solutions to the downstream and midstream energy markets. The results of the acquired business are generally included in Quanta’s Oil and Gas Infrastructure Services segment and have been included in Quanta’s consolidated financial statements beginning on the acquisition date. During the year ended December 31, 2017 , Quanta also acquired a communications infrastructure services contractor and an electrical and communications contractor, both of which are located in the United States. The results of these acquired businesses are generally included in Quanta’s Electric Power Infrastructure Services segment and have been included in Quanta’s consolidated financial statements beginning on the respective acquisition dates. During 2016 and 2015, Quanta completed five and 11 acquisitions. The results have been included in Quanta’s consolidated financial statements beginning on the respective acquisition dates. See further discussion regarding these acquisitions in Note 5. Disposition - Fiber Optic Licensing Operations On April 29, 2015 , Quanta entered into a stock purchase agreement with Crown Castle International Corp. (Crown Castle) pursuant to which Quanta agreed to sell its fiber optic licensing operations. The purchase agreement contained customary representations and warranties, covenants and indemnities. On August 4, 2015 , Quanta completed the sale for a purchase price of $1.00 billion in cash, resulting in after-tax net proceeds of $848.2 million . In the third quarter of 2015, Quanta recognized a net of tax gain of $171.0 million . Quanta has presented the results of operations, financial position, cash flows and disclosures of the fiber optic licensing operations as discontinued operations for all periods in the accompanying consolidated financial statements. These results were included in Quanta’s Fiber Optic Licensing and Other segment prior to the second quarter of 2015.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES: Principles of Consolidation The consolidated financial statements of Quanta include the accounts of Quanta Services, Inc. and its wholly owned subsidiaries, which are also referred to as its operating units. The consolidated financial statements also include the accounts of certain of Quanta’s investments in joint ventures, which are either consolidated or proportionately consolidated, as discussed in the following summary of significant accounting policies. Investments in affiliated entities in which Quanta does not have a controlling financial interest, but over which Quanta has significant influence, usually because Quanta holds a voting interest of between 20% and 50%, are accounted for using the equity method. All significant intercompany accounts and transactions have been eliminated in consolidation. Unless the context requires otherwise, references to Quanta include Quanta Services, Inc. and its consolidated subsidiaries. Reclassifications Quanta reclassified certain prior period amounts related to stock-based compensation in the accompanying consolidated statements of cash flows to conform to the current period presentation under a recently adopted accounting update. Additionally, certain reclassifications have been made to Quanta’s prior year’s consolidated statements of operations to conform to classifications in the current year. Use of Estimates and Assumptions The preparation of financial statements in conformity with US GAAP requires the use of estimates and assumptions by management in determining the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities known to exist as of the date the financial statements are published, and the reported amounts of revenues and expenses recognized during the periods presented. Quanta reviews all significant estimates affecting its consolidated financial statements on a recurring basis and records the effect of any necessary adjustments prior to their publication. Judgments and estimates are based on Quanta’s beliefs and assumptions derived from information available at the time such judgments and estimates are made. Uncertainties with respect to such estimates and assumptions are inherent in the preparation of financial statements. Estimates are primarily used in Quanta’s assessment of the allowance for doubtful accounts, valuation of inventory, useful lives of assets, fair value assumptions in analyzing goodwill, other intangibles and long-lived asset impairments, equity and other investments, loan receivables, purchase price allocations, acquisition-related contingent consideration liabilities, liabilities for insurance and other claims and guarantees, multiemployer pension plan withdrawal liabilities, revenue recognition for construction contracts inclusive of contractual change orders and claims, share-based compensation, operating results of reportable segments, as well as the provision for income taxes and the calculation of uncertain tax positions. Cash and Cash Equivalents Quanta had cash and cash equivalents of $138.3 million and $112.2 million as of December 31, 2017 and 2016 . Cash consisting of interest-bearing demand deposits is carried at cost, which approximates fair value. Quanta considers all highly liquid investments with an original maturity of three months or less at the time of purchase to be cash equivalents, which are carried at fair value. At December 31, 2017 and 2016 , cash equivalents were $7.1 million and $8.8 million and consisted primarily of money market investments and money market mutual funds and are discussed further in Fair Value Measurements below. As of December 31, 2017 and 2016 , cash and cash equivalents held in domestic bank accounts were $83.1 million and $19.5 million , and cash and cash equivalents held in foreign bank accounts were $55.2 million and $92.7 million . As of December 31, 2017 and 2016 , cash and cash equivalents held by joint ventures, which are either consolidated or proportionately consolidated, were $16.7 million and $11.5 million , of which $10.0 million and $10.0 million related to domestic joint ventures. Cash and cash equivalents held by the joint ventures are available to support joint venture operations, but Quanta cannot utilize those assets to support its other operations. Quanta generally has no right to the joint ventures’ cash and cash equivalents other than participating in distributions and in the event of dissolution. Current and Long-Term Accounts and Notes Receivable and Allowance for Doubtful Accounts Quanta provides an allowance for doubtful accounts when collection of an account or note receivable is considered doubtful, and receivables are written off against the allowance when deemed uncollectible. Inherent in the assessment of the allowance for doubtful accounts are certain judgments and estimates regarding, among other factors, the customer’s access to capital, the customer’s willingness or ability to pay, general economic and market conditions, the ongoing relationship with the customer and uncertainties related to the resolution of disputed matters. Quanta considers accounts receivable delinquent after 30 days but does not generally include delinquent accounts in its analysis of the allowance for doubtful accounts unless the accounts receivable have been outstanding for at least 90 days. Quanta also includes accounts receivable balances that relate to customers in bankruptcy or with other known difficulties in its analysis of the allowance for doubtful accounts. Material changes in customers’ business or cash flows, which may be impacted by negative economic and market conditions, could affect Quanta’s ability to collect amounts due. As of December 31, 2017 and 2016 , Quanta had allowances for doubtful accounts on current receivables of $4.5 million and $2.8 million . Long-term accounts receivable are included within “Other assets, net” in the accompanying consolidated balance sheets. Should customers experience financial difficulties or file for bankruptcy, or should anticipated recoveries relating to receivables in existing bankruptcies or other workout situations fail to materialize, Quanta could experience reduced cash flows and losses in excess of current allowances provided. The balances billed but not paid by customers pursuant to retainage provisions in certain contracts are generally due upon completion of the contracts and acceptance by the customer. Based on Quanta’s experience with similar contracts in recent years, the majority of the retainage balances at each balance sheet date are expected to be collected within the next twelve months. Current retainage balances as of December 31, 2017 and 2016 were $300.5 million and $231.0 million and were included in “Accounts receivable.” Retainage balances with settlement dates beyond the next twelve months were included in “Other assets, net,” and as of December 31, 2017 and 2016 were $41.9 million and $5.2 million . Within accounts receivable, Quanta recognizes unbilled receivables in circumstances such as when revenues have been earned and recorded but the amount cannot be billed under the terms of the contract until a later date; costs have been incurred but are yet to be billed under cost-reimbursement type contracts; or amounts arise from routine lags in billing (for example, work completed one month but not billed until the next month). These balances do not include revenues accrued for work performed under fixed-price contracts as these amounts are recorded as “Costs and estimated earnings in excess of billings on uncompleted contracts.” At December 31, 2017 and 2016 , the balances of unbilled receivables included in “Accounts receivable” were $303.9 million and $206.8 million . Inventories Inventories consist primarily of parts and supplies held for use in the ordinary course of business, which are valued by Quanta at the lower of cost or net realizable value. Cost is determined by using either the first-in, first-out (FIFO) method or the average costing method. Inventories also include certain job specific materials not yet installed which are valued using the specific identification method. Property and Equipment Property and equipment are stated at cost, and depreciation is computed using the straight-line method, net of estimated salvage values, over the estimated useful lives of the assets. Leasehold improvements are capitalized and amortized over the lesser of the life of the lease or the estimated useful life of the asset. Depreciation expense related to property and equipment was $183.8 million , $170.2 million and $162.8 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Accrued capital expenditures were $9.6 million and $12.7 million as of December 31, 2017 and 2016 . The impact of these items has been excluded from Quanta’s capital expenditures in the accompanying consolidated statements of cash flows due to their non-cash nature. Expenditures for repairs and maintenance are charged to expense when incurred. Expenditures for major renewals and betterments, which extend the useful lives of existing equipment, are capitalized and depreciated over the adjusted remaining useful lives of the assets. Upon retirement or disposition of property and equipment, the cost and related accumulated depreciation are removed from the accounts and any resulting gain or loss is reflected in selling, general and administrative expenses. Management reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount may not be realizable. Quanta also recorded asset impairments primarily related to certain international renewable energy services operations of $8.0 million in 2016 and $6.6 million in 2015. The 2016 impairment was primarily due to a pending disposition of certain international renewable energy services operations that was completed in 2017, and the 2015 impairment was based on the estimated future undiscounted cash flows for the asset group as compared to their carrying amount. When an evaluation is required, the estimated future undiscounted cash flows associated with the asset group are compared to the asset group’s carrying amount to determine if an impairment of such asset group is necessary. The effect of any impairment involves expensing the difference between the fair value of such asset group and its carrying amount in the period incurred. Other Assets, Net Other assets, net consists primarily of long-term receivables, long-term retainage, deferred tax assets, debt issuance costs, equity and other investments, refundable security deposits for leased properties and insurance claims in excess of deductibles that are due from Quanta’s insurers. Debt Issuance Costs Capitalized debt issuance costs related to Quanta’s senior secured revolving credit facility and any other debt outstanding at a given balance sheet date are included in other assets, net and are amortized into interest expense on a straight-line basis over the terms of the respective agreements giving rise to the debt issuance costs, which Quanta believes approximates the effective interest rate method. During 2017 and 2015, Quanta incurred $1.5 million and $3.8 million of debt issuance costs related to amendments and a restatement of its credit agreement. In 2017 and 2015, Quanta recorded a nominal charge to interest expense for the write-off of a portion of the debt issuance costs related to the prior facility. As of December 31, 2017 and 2016 , capitalized debt issuance costs were $12.9 million and $11.4 million , with accumulated amortization of $7.4 million and $6.0 million . For the years ended December 31, 2017 , 2016 and 2015 , amortization expense related to capitalized debt issuance costs was $1.3 million , $1.4 million and $1.3 million , respectively. Goodwill Quanta has recorded goodwill in connection with its historical acquisitions of companies. Upon acquisition, these companies were either combined into one of Quanta’s existing operating units or managed on a stand-alone basis as an individual operating unit. Goodwill recorded in connection with these acquisitions is subject to an annual assessment for impairment, which Quanta performs at the operating unit level for each operating unit that carries a balance of goodwill. Each of Quanta’s operating units is organized into one of two internal divisions: the Electric Power Infrastructure Services Division and the Oil and Gas Infrastructure Services Division. As most of the companies acquired by Quanta provide multiple types of services for multiple types of customers, these divisional designations are based on the predominant type of work performed by each operating unit at the point in time the divisional designation is made. Goodwill is required to be measured for impairment at the reporting unit level, which represents the operating segment level or one level below the operating segment level for which discrete financial information is available. Quanta has determined that its individual operating units represent its reporting units for the purpose of assessing goodwill impairments. In January 2017, the Financial Accounting Standards Board (FASB) issued an update intended to simplify the subsequent measurement of goodwill by eliminating the second step in the two-step goodwill impairment test. The update requires an entity to perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and to recognize an impairment charge for the amount by which the carrying amount exceeds the fair value. The income tax effect associated with an impairment of tax deductible goodwill is also considered in the measurement of the goodwill impairment. Quanta elected to adopt the provisions of the update in connection with its annual impairment test performed in the fourth quarter of 2017. Quanta has the option to first assess qualitative factors to determine whether it is necessary to perform the quantitative fair value-based impairment test described below. If Quanta believes that, as a result of its qualitative assessment, it is more likely than not that the fair value of a reporting unit is less than its carrying amount, the quantitative impairment test is required. Quanta can choose to perform the qualitative assessment on none, some, or all of its reporting units. Quanta can also bypass the qualitative assessment for any reporting unit in any period and proceed directly to the quantitative impairment test, and then resume the qualitative assessment in any subsequent period. Qualitative indicators including deterioration in macroeconomic conditions, declining financial performance, or a sustained decrease in share price, among other things, may trigger the need for annual or interim impairment testing of goodwill associated with one or all of the reporting units. Quanta’s annual goodwill impairment assessment is performed in the fourth quarter of its fiscal year, or more frequently if events or circumstances arise which indicate that goodwill may be impaired. For instance, a decrease in Quanta’s market capitalization below book value, a significant change in business climate or loss of a significant customer, as well as the qualitative indicators referenced above, may trigger the need for interim impairment testing of goodwill for a reporting unit. The quantitative impairment test involves comparing the fair value of each of Quanta’s reporting units with its carrying amount, including goodwill. If the carrying amount of a reporting unit exceeds its fair value, an impairment loss is recorded as a reduction to goodwill with a corresponding charge to “Asset impairment charges” in the accompanying consolidated statements of operations. Any goodwill impairment is limited to the total amount of goodwill allocated to that reporting unit. Quanta determines the fair value of its reporting units using a weighted combination of the discounted cash flow, market multiple and market capitalization valuation approaches, with heavier weighting on the discounted cash flow method because management believes this method results in the most accurate calculation of fair value. Determining the fair value of a reporting unit requires judgment and the use of significant estimates and assumptions, including revenue growth rates, operating margins, discount rates, weighted average costs of capital and future market conditions. Quanta believes the estimates and assumptions used in its impairment assessments are reasonable and based on available market information, but variations in any of the assumptions could result in materially different calculations of fair value and determinations of whether or not an impairment is indicated. Under the discounted cash flow method, Quanta determines fair value based on the estimated future cash flows of each reporting unit, discounted to present value using risk-adjusted industry discount rates, which reflect the overall level of inherent risk of a reporting unit and the rate of return an outside investor would expect to earn. Cash flow projections are derived from budgeted amounts and operating forecasts (typically a one-year model) plus an estimate of later period cash flows, all of which are evaluated by management. Subsequent period cash flows are developed for each reporting unit using growth rates that management believes are reasonably likely to occur, along with a terminal value derived from the reporting unit’s earnings before interest, taxes, depreciation and amortization (EBITDA). The EBITDA multiples for each reporting unit are based on trailing twelve-month comparable industry data. Under the market multiple and market capitalization approaches, Quanta determines the estimated fair value of each of its reporting units by applying transaction multiples to each reporting unit’s projected EBITDA and then averaging that estimate with similar historical calculations using either a one, two or three year average. For the market capitalization approach, Quanta adds a reasonable control premium, which is estimated as the premium that would be received in a sale of the reporting unit in an orderly transaction between market participants. The projected cash flows and estimated levels of EBITDA by reporting unit were used to determine fair value under the three approaches discussed herein. The following table presents the significant estimates used by management in determining the fair values of Quanta’s reporting units at December 31, 2017 , 2016 and 2015 : 2017 2016 2015 Years of cash flows before terminal value 5 years 5 years 5 years Discount rates 12.0% to 14.0% 12.5% to 14.5% 12.0% to 16.0% EBITDA multiples 5.5 to 7.0 5.5 to 7.0 5.0 to 6.5 Weighting of three approaches: Discounted cash flows 70% 70% 70% Market multiple 15% 15% 15% Market capitalization 15% 15% 15% For recently acquired reporting units, a quantitative impairment test may indicate a fair value that is substantially similar to the reporting unit’s carrying amount. Such similarities in value are generally an indication that management’s estimates of future cash flows associated with the recently acquired reporting unit remain relatively consistent with the assumptions that were used to derive its initial fair value. During the fourth quarter of 2017 , a quantitative fair-value based goodwill impairment analysis was performed for each of Quanta’s reporting units, and no reporting units were evaluated solely on a qualitative basis. The analysis indicated that the fair value of each of Quanta’s reporting units, with the exception of two reporting units in its Oil and Gas Infrastructure Services Division, was in excess of its carrying amount. Quanta recorded a $57.0 million non-cash charge in the fourth quarter of 2017 for the impairment of goodwill associated with the two reporting units. Specifically, a reporting unit that provides material handling services experienced lower operating margins and is expected to continue to face a highly competitive environment in its select markets and a reporting unit that provides marine and offshore services experienced prolonged periods of reduced revenues and operating margins and is expected to continue to experience lower levels of activity in the U.S. Gulf of Mexico and other offshore markets. As discussed generally above, when evaluating the 2017 quantitative impairment test results, management considered many factors in determining whether an impairment of goodwill for any reporting unit was reasonably likely to occur in future periods, including future market conditions and the economic environment. Additionally, management considered the sensitivity of its fair value estimates to changes in certain valuation assumptions. After taking into account a 10% decrease in the fair value of each of Quanta’s reporting units, one additional reporting unit within Quanta’s Oil and Gas Infrastructure Services Division would have a fair value below its carrying amount. The fair value determined in 2017 for this reporting unit was consistent with the fair value determined in 2016 . Circumstances such as market declines, unfavorable economic conditions, loss of a major customer or other factors could increase the risk of impairment of goodwill for this reporting unit in future periods. If an operating unit experiences prolonged periods of declining revenues, operating margins or both, it may be at risk of failing the quantitative goodwill impairment test. In addition to the reporting units referenced above, certain operating units have experienced declines over the short-term due to challenging macroeconomic conditions in certain geographic areas and low oil and natural gas prices, which have negatively impacted customer spending and resulted in project cancellations and delays. Additionally, customer capital spending has been constrained as a result of an increasingly complex regulatory and permitting environment. Certain operating units within Quanta’s Oil and Gas Infrastructure Services Division that primarily operate within the midstream and smaller-scale transmission market, including the reporting unit referenced above, have continued to be negatively impacted by these factors. Goodwill and intangible assets associated with these operating units were $50.1 million and $14.7 million at December 31, 2017 . Quanta monitors these conditions and others to determine if it is necessary to perform the quantitative fair-value based impairment test for one or more operating units prior to the annual impairment assessment. Although Quanta is not aware of circumstances that would lead to additional goodwill impairments at this time, circumstances such as a continued market decline, the loss of a major customer or other factors could impact the valuation of goodwill in the future. The goodwill analysis performed for each reporting unit was based on estimates and comparisons obtained from the electric power and oil and gas industries. Quanta assigned a higher weighting to the discounted cash flow approach in all periods to reflect increased expectations of market value being determined from a “held and used” model. As stated previously, cash flows are derived from budgeted amounts and operating forecasts that have been evaluated by management. In connection with the 2017 assessment, reporting unit annual compounded revenue growth rates during the cash flow projection period varied from negative 14% to positive 17% . Estimating future cash flows requires significant judgment, and Quanta’s projections may vary from cash flows eventually realized. Changes in Quanta’s judgments and projections could result in a significantly different estimate of the fair values of reporting units and intangible assets and could result in an impairment. Variances in the assessment of market conditions, projected cash flows, cost of capital, growth rates and acquisition multiples applied could have an impact on the assessment of impairments and the amount of any goodwill impairment charges recorded. For example, lower growth rates, lower acquisition multiples or higher costs of capital assumptions would all individually lead to lower fair value assessments and potentially increased frequency or size of goodwill impairments. Goodwill impairments are included within “Asset impairment charges” on Quanta’s consolidated statements of operations. Based on the goodwill impairment analysis, Quanta compared the sum of fair values of its reporting units to its market capitalization at December 31, 2017 and determined that the excess of the aggregate fair value of all reporting units to its market capitalization reflected a reasonable control premium. Quanta’s market capitalization at December 31, 2017 was approximately $6.02 billion , and its total stockholders’ equity was approximately $3.79 billion . If the price of Quanta’s common stock were to decline to a level that causes its market capitalization to be lower than the value of its stockholders’ equity, this would be another factor that could increase the risk of further impairment of goodwill in future periods. Increases in the carrying amount of individual reporting units that may be indicated by Quanta’s impairment tests are not recorded, therefore Quanta may record goodwill impairments in the future, even when the aggregate fair value of its reporting units as a whole may increase. During the fourth quarter of 2015, management concluded that goodwill was impaired at two reporting units in Quanta’s Oil and Gas Infrastructure Services Division and recorded a $39.8 million non-cash charge for the impairment of goodwill, which primarily resulted from lower levels of expected activity in the U.S. Gulf of Mexico and, to a lesser extent, the extended low commodity price environment for certain directional drilling operations in Australia. Other Intangible Assets Quanta’s intangible assets include customer relationships, backlog, trade names, non-compete agreements, patented rights and developed technology, all of which are subject to amortization. The value of customer relationships is estimated as of the date a business is acquired based on the value-in-use concept utilizing the income approach, specifically the excess earnings method. This analysis discounts to present value the projected cash flows attributable to the customer relationships, with consideration given to customer contract renewals and estimated customer attrition rates. The following table presents the significant estimates used by management in determining the fair values of customer relationships associated with acquisitions in the years ended December 31, 2017 , 2016 and 2015 : 2017 2016 2015 Discount rates 17% to 25% 20% to 23% 18% to 22% Customer attrition rates 15% to 78% 10% to 70% 14% to 70% Quanta values backlog for acquired businesses as of the acquisition date based upon the contractual nature of the backlog within each service line, discounted to present value. The value of trade names is estimated using the relief-from-royalty method of the income approach. This approach is based on the assumption that in lieu of ownership, a company would be willing to pay a royalty for use of the trade name. Quanta amortizes intangible assets based upon the estimated consumption of their economic benefits, or on a straight-line basis if the pattern of economic benefit cannot otherwise be reliably estimated. Intangible assets subject to amortization are reviewed for impairment and tested for recoverability whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. For instance, a significant change in business climate or a loss of a significant customer, among other things, may trigger the need for interim impairment testing of intangible assets. An impairment loss is recognized if the carrying amount of an intangible asset is not recoverable and its carrying amount exceeds its fair value. Intangible asset impairments are included within “Asset impairment charges” in the accompanying consolidated statements of operations. During the fourth quarter of 2017, Quanta recorded an impairment charge of $1.1 million related to a customer relationship intangible asset, which primarily resulted from a strategic decision to restructure a business within a reporting unit in the Oil and Gas Infrastructure Services Division. During the fourth quarter of 2015, Quanta recorded an impairment charge of $12.1 million related to customer relationship, trade name and non-compete agreement intangible assets, which primarily resulted from lower levels of expected activity in the U.S. Gulf of Mexico and, to a lesser extent, the extended low commodity price environment for certain directional drilling operations in Australia. The two reporting units impacted also had related goodwill impairments, as discussed above, and are in Quanta’s Oil and Gas Infrastructure Services Division. Investments in Affiliates and Other Entities In the normal course of business, Quanta enters into various types of investment arrangements, each having unique terms and conditions. These investments may include equity interests held by Quanta in business entities, including general or limited partnerships, contractual joint ventures, or other forms of equity or profit participation. These investments may also include Quanta’s participation in different financing structures, such as the extension of loans to project specific entities, the acquisition of convertible notes issued by project specific entities, or other strategic financing arrangements. Quanta also enters into strategic partnerships with customers and infrastructure investors to provide fully integrated infrastructure services on certain projects, including planning and feasibility analyses, engineering, design, procurement, construction and project operation and maintenance. These projects include public-private partnerships, private infrastructure projects and concessions, along with build, own, operate and transfer and build-to-suit arrangements. As part of this strategy, during the year ended December 31, 2017, Quanta formed a partnership with select investors that provides up to $1.0 billion of capital, including approximately $80.0 million from Quanta, available to invest in certain of these infrastructure projects through August 2024. Wholly owned subsidiaries of Quanta serve as the general partner of this partnership and as a separately operated registered investment adviser that manages the invested capital. Quanta determines whether investments involve a variable interest entity (VIE) based on the characteristics of the subject entity. If the entity is determined to be a VIE, then management determines if Quanta is the primary beneficiary of the entity and whether or not consolidation of the VIE is required. The primary beneficiary consolidating the VIE must normally have both (i) the power to direct the activities that most significantly affect the VIE’s economic performance and (ii) the obligation to absorb significant losses of or the right to receive significant benefits from the VIE. When Quanta is deemed to be the primary beneficiary, the VIE is consolidated and the other party’s equity interest in the VIE is accounted for as a non-controlling interest. In cases where Quanta determines that it has an undivided interest in the assets, liabilities, revenues and profits of an unincorporated VIE (e.g., a general partnership interest), such amounts are consolidated on a basis proportional to Quanta’s ownership interest in the unincorporated entity. Investments in entities of which Quanta is not the primary beneficiary, but over which Quanta has the ability to exercise significant influence, are accounted for using the equity method of accounting. Quanta’s share of net income or losses from unconsolidated equity investments is reported as equity in earnings (losses) of unconsolidated affiliates, which is included in “Other income (expense)” in the accompanying consolidated statements of operations. Equity investments are reviewed for impairment by assessing whether any decline in the fair value of the investment below the carrying amount is other than temporary. In making this determination, factors such as the ability to recover the carrying amount of the investment and the inability of the investee to sustain an earnings capacity are evaluated in determining whether a loss in value should be recognized. Any impairment losses related to investments would be recognized in equity in earnings (losses) of unconsolidated affiliates. Equit

New Accounting Pronouncements

New Accounting Pronouncements	12 Months Ended
	Dec. 31, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Pronouncements	NEW ACCOUNTING PRONOUNCEMENTS: Adoption of New Accounting Pronouncements In July 2015 , the FASB issued an update that requires inventory to be measured at the lower of either cost or net realizable value. When evidence exists that the net realizable value of inventory is lower than its cost, the difference will be recognized as a loss in earnings in the period in which it occurs. Quanta adopted this guidance effective January 1, 2017 , and the adoption of the update did not have a significant impact on its consolidated financial statements or related disclosures. In March 2016 , the FASB issued an update that amends the accounting for share-based payments in several key areas, including the treatment and cash flow presentation of tax effects related to the settlement of share-based payments and the accounting for forfeitures of share-based awards. The new guidance requires companies with share-based payments to record all related tax effects at settlement (or expiration) through income tax expense on the statement of operations rather than through additional paid-in capital (APIC) within equity. This update also requires excess tax benefits to be classified as an operating activity on the statement of cash flows rather than classified as a financing activity and requires cash paid by an employer when withholding shares for the employee portion of taxes to be presented as a financing activity. The update also allows companies to either account for forfeitures of share-based payments as they occur or to estimate forfeitures. This guidance is required to be applied prospectively except for the classification of cash related to tax withholding, which requires retrospective application. Quanta adopted this guidance effective January 1, 2017 and will continue to estimate forfeitures of share-based payments. Quanta experienced increased volatility of income tax expense after adoption of this guidance and anticipates that trend to continue. During the year ended December 31, 2017 , Quanta recorded income tax benefits of $5.1 million related to the settlement of share-based awards. APIC was not adjusted for amounts recorded prior to 2017, and therefore Quanta’s retained earnings were not affected by the adoption of this guidance. Additionally, $8.3 million and $9.8 million were reclassified from operating activities to financing activities on the statements of cash flows for the years ended December 31, 2016 and 2015 associated with cash paid by Quanta to satisfy tax withholding obligations for share-settled awards. Further, the presentation of excess tax benefits on the statements of cash flows is now shown as cash flows from operating activities rather than in financing activities. The excess tax benefits reclassified to operating activities for each of the years ended December 31, 2016 and 2015 was $0.7 million . In October 2016 , the FASB issued an update that amends the consolidation guidance related to how a reporting entity that is the single decision maker of a VIE should treat indirect interests in the VIE held through related parties that are under common control with the reporting entity when determining whether it is the primary beneficiary of a VIE. A reporting entity has an indirect interest in a VIE if it has a direct interest in a related party that, in turn, has a direct interest in the VIE. Quanta adopted this guidance effective January 1, 2017 , and the adoption of the update did not have a significant impact on its consolidated financial statements or related disclosures. In January 2017 , the FASB issued an update intended to simplify the subsequent measurement of goodwill by eliminating the second step in the two-step goodwill impairment test. As permitted under this guidance, Quanta elected to adopt this guidance for its annual goodwill impairment test during the fourth quarter of 2017 (see Note 2 for further detail on this update and a description of the quantitative goodwill impairment test). Accounting Standards Not Yet Adopted To be adopted effective January 1, 2018: In May 2014 , the FASB issued an update that supersedes most current revenue recognition guidance, as well as certain cost recognition guidance. The update, together with other clarifying updates, requires that the recognition of revenue related to the transfer of goods or services to customers reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The update also requires new qualitative and quantitative disclosures about the nature, amount, timing and uncertainty of revenues and cash flows arising from customer contracts, including significant judgments and changes in judgments, information about contract balances and performance obligations, and assets recognized from costs incurred to obtain or fulfill a contract. The new guidance is effective for fiscal years beginning on or after December 15, 2017 and can be applied on a full retrospective or modified retrospective basis, whereby the entity records a cumulative effect of initially applying this update at the date of initial application. Quanta will adopt the new revenue recognition guidance using the modified retrospective transition method effective for the quarter ending March 31, 2018, applying the guidance to contracts that were not substantially complete as of January 1, 2018 . Quanta’s financial results for reporting periods after January 1, 2018 will be presented under the new guidance, while financial results for prior periods will continue to be reported in accordance with the prior guidance and Quanta’s historical accounting policy. Quanta has substantially completed its evaluation of the impact of the new guidance on its contracts with customers, including identification of differences that will result from the new requirements. Based on this evaluation, we estimate that the net cumulative adjustment to retained earnings from adoption as of January 1, 2018 , will be less than $10.0 million . With respect to ongoing revenues generated from master service agreements, repair and maintenance contracts and fixed price and non-fixed price installation contracts, Quanta does not anticipate any significant changes to the pattern of revenue recognition and does not believe that the guidance surrounding identification of contracts and performance obligations or measurement of variable consideration will have a material impact on the revenue recognition for these arrangements. Quanta expects its disclosures related to revenue recognition will expand to address new quantitative and qualitative requirements regarding the nature, amount and timing of revenue from contracts and additional information related to contract assets and liabilities. In January 2016 , the FASB issued an update that addresses certain aspects of recognition, measurement, presentation, and disclosure of financial instruments to provide users of financial statements with more decision-useful information. This update requires equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. However, an entity may choose to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. The new standard is effective for interim and annual periods beginning after December 15, 2017 , and Quanta will adopt the new standard effective January 1, 2018 . Quanta’s equity investments that are within the scope of this update do not have readily determinable fair values. Accordingly, Quanta intends to continue to measure these investments at cost less any impairments and will also consider changes resulting from any observable price changes as described above. The new standard is not expected to have a material impact on Quanta’s consolidated financial statements in the near-term based on the equity investments it held as of December 31, 2017 . In August 2016 , the FASB issued an update intended to standardize the classification of certain transactions on the statements of cash flows . These transactions include contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies and distributions received from equity method investments. The new standard is effective for interim and annual reporting periods beginning after December 15, 2017 and requires application using a retrospective transition method. Quanta will adopt this guidance effective January 1, 2018 and does not expect it to have a material impact on its consolidated financial statements. In October 2016 , the FASB issued an update that will require a reporting entity to recognize the tax expense from the sale of an asset in the seller’s tax jurisdiction when the transfer occurs, even though the pre-tax effects of that transaction are eliminated in consolidation. Any deferred tax asset that arises in the buyer’s jurisdiction would also be recognized at the time of the transfer. The new guidance will not apply to intra-entity transfers of inventory. The income tax consequences from the sale of inventory from one member of a consolidated entity to another will continue to be deferred until the inventory is sold to a third party. The new standard is effective for interim and annual reporting periods beginning after December 15, 2017 . The modified retrospective method will be required for transition to the new guidance, with a cumulative-effect adjustment recorded in retained earnings as of the beginning of the period of adoption, if applicable. Quanta will adopt this guidance effective January 1, 2018 and does not expect it to have a material impact on its consolidated financial statements. In November 2016 , the FASB issued an update intended to standardize the classification of restricted cash and cash equivalents transactions on the statement of cash flows . The new guidance requires net cash withdrawn from (deposited to) restricted cash to be removed from investing activities of continuing operations. Additionally, restricted cash balances for each period will be included with “Cash and cash equivalents” in order to obtain beginning and ending balances for consolidated statement of cash flow purposes, and any activity between “Cash and cash equivalents” and restricted cash will no longer be reported on Quanta’s consolidated statements of cash flows. The new standard is effective for interim and annual reporting periods beginning after December 15, 2017 . The retrospective transition method will be required for this new guidance. Quanta will adopt this guidance effective January 1, 2018 and does not expect it to have a material impact on its consolidated financial statements. In January 2017 , the FASB issued an update intended to clarify whether transactions should be accounted for as acquisitions or disposals of assets or business es. When substantially all of the fair value of the gross assets acquired or disposed of is concentrated in a single identifiable asset or group of similar identifiable assets, the asset or group is not a business. The update will require, among other things, that to be considered a business, a set of assets and activities must include, at a minimum, an input and a substantive process that together significantly contribute to the ability to create output. Additionally, the update removes the evaluation of whether a market participant could replace missing elements in order to consider the set of assets and activities a business, provides more stringent criteria for sets without outputs and narrows the definition of output. The update is effective for interim and annual reporting periods beginning after December 15, 2017 , and the prospective transition method will be required for this new guidance. Accordingly, Quanta will adopt this guidance effective January 1, 2018 and does not expect it to impact its consolidated financial statements prior to such date. In May 2017 , the FASB issued an update providing guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. A modification should be accounted for unless the following characteristics of the award are unchanged: the fair value, the vesting conditions and the classification as an equity instrument or a liability instrument. The update is effective for interim and annual periods beginning after December 15, 2017 and is required to be applied prospectively. Accordingly, Quanta will adopt this guidance effective January 1, 2018 and does not expect it to impact its consolidated financial statements prior to such date. To be adopted subsequent to January 1, 2018: In February 2016 , the FASB issued an update that requires companies to recognize on the balance sheet the contractual right to use assets and liabilities corresponding to the rights and obligations created by lease contracts. The new standard is effective for interim and annual periods beginning after December 15, 2018 . While Quanta continues to evaluate the effect of the standard on its consolidated financial statements, it is anticipated that the adoption of the standard will materially impact its consolidated balance sheets. Quanta will adopt this guidance by January 1, 2019 . In June 2016 , the FASB issued an update that will change the way companies measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The update will require companies to use an “expected loss” model for instruments measured at amortized cost and to record allowances for available-for-sale debt securities rather than reduce the carrying amounts. The update will also require disclosure of information regarding how a company developed its allowance, including changes in the factors that influenced management’s estimate of expected credit losses and the reasons for those changes. Companies will apply this standard’s provisions as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. The new standard is effective for interim and annual reporting periods beginning after December 15, 2019 . Quanta is currently evaluating the potential impact of this authoritative guidance on its consolidated financial statements and will adopt this guidance by January 1, 2020 . In August 2017 , the FASB issued an update which amends and simplifies existing guidance for presenting the economic effects of risk management activities in the financial statements. The update is effective for interim and annual periods beginning after December 15, 2018 . The amended presentation and disclosure guidance is required only prospectively, but certain amendments, if applicable, could require a cumulative-effect adjustment. Quanta is evaluating the impact of this new standard on its consolidated financial statements and will adopt the new standard by January 1, 2019 ; however, as of December 31, 2017 , Quanta had no hedging relationships outstanding.

Discontinued Operations

Discontinued Operations	12 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	DISCONTINUED OPERATIONS: On August 4, 2015 , Quanta completed the sale of its fiber optic licensing operations to Crown Castle for an aggregate purchase price of $1.00 billion in cash, resulting in estimated after-tax net proceeds of $848.2 million . In the third quarter of 2015, Quanta recognized a pre-tax gain of $271.8 million and a corresponding tax expense of $100.8 million , which resulted in a gain on the sale, net of tax, of $171.0 million . Quanta remains liable for all taxes and insured claims associated with the fiber optic licensing operations arising on or before or outstanding as of August 4, 2015 . Quanta has presented the results of operations, financial position, cash flows and disclosures related to its fiber optic licensing operations as discontinued operations in the accompanying consolidated financial statements. The results were included in Quanta’s Fiber Optic Licensing and Other segment prior to the second quarter of 2015. The following represents a reconciliation of the major classes of line items constituting income from discontinued operations primarily related to Quanta’s fiber optic licensing operations to the accompanying consolidated statements of operations (in thousands): Year Ended December 31, 2016 2015 Major classes of line items constituting pretax income from discontinued operations: Revenues $ — $ 59,998 Expenses: Cost of services (including depreciation) — 24,748 Selling, general and administrative expenses (980 ) 12,047 Amortization of intangible assets — 963 Other income (expense) items that are not major — 10 Net income before taxes of discontinued operations related to fiber optic licensing operations related to major classes of income before taxes 980 22,250 Pretax gain on the disposal of the fiber optic licensing operations — 271,833 Total pretax gain on fiber optic licensing operations 980 294,083 Provision for income taxes related to fiber optic licensing operations 667 103,462 Net income from discontinued operations related to fiber optic licensing operations 313 190,621 Net loss from discontinued operations related to telecommunication operations (655 ) — Net income (loss) from discontinued operations as presented in the accompanying consolidated statements of operations $ (342 ) $ 190,621 There were no assets or liabilities associated with fiber optic licensing operations at December 31, 2017 or 2016 . Additionally, on December 3, 2012 , Quanta sold substantially all of its domestic telecommunications infrastructure services operations and related subsidiaries. During the year ended December 31, 2016, legal fees of $1.0 million were recorded related to an ongoing legal matter associated with these discontinued operations. See Legal Proceedings — Lorenzo Benton v. Telecom Network Specialists, Inc., et al. in Note 15 for additional information. The aggregate net of tax impact of these legal fees was $0.7 million during the year ended December 31, 2016.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions	ACQUISITIONS: 2017 Acquisitions On July 20, 2017, Quanta acquired Stronghold, a specialized services business located in the United States that provides high-pressure and critical-path solutions to the downstream and midstream energy markets. The aggregate consideration included $351.0 million in cash, subject to certain adjustments, and 2,693,680 shares of Quanta common stock, which had a fair value of $81.3 million at the acquisition date. Additionally, the acquisition includes the potential payment of up to $100.0 million of contingent consideration, payable if the acquired business achieves certain financial targets over a three -year period. Based on the estimated fair value of this contingent consideration, Quanta recorded a $51.1 million liability as of the acquisition date. The results of the acquired business have generally been included in Quanta’s Oil and Gas Infrastructure Services segment and consolidated financial statements since the acquisition date. During the year ended December 31, 2017 , Quanta also acquired a communications infrastructure services contractor and an electrical and communications contractor, both of which are located in the United States. The aggregate consideration for these acquisitions consisted of $11.9 million paid or payable in cash, subject to certain adjustments, and 288,666 shares of Quanta common stock, with a value of $8.3 million as of the respective acquisition dates. The results of the acquired businesses have generally been included in Quanta’s Electric Power Infrastructure Services segment and consolidated financial statements since the acquisition dates. Quanta is in the process of finalizing its assessments of the fair values of the acquired assets and assumed liabilities related to businesses acquired during 2017 , and further adjustments to the purchase price allocations may occur. As of December 31, 2017 , the estimated fair values of the net assets acquired were preliminary, with possible updates primarily related to certain tax estimates. The aggregate purchase consideration of the businesses acquired during 2017 was preliminarily allocated to acquired assets and assumed liabilities, which resulted in an allocation of $97.4 million to net tangible assets, $103.8 million to identifiable intangible assets and $302.4 million to goodwill. 2016 Acquisitions During 2016, Quanta completed five acquisitions. The results of four of the acquired businesses are generally included in Quanta’s Electric Power Infrastructure Services segment. These businesses included an electrical infrastructure services business located in Australia, a utility contracting business located in Canada, a full service medium- and high-voltage powerline contracting business located in the United States and a communications services business located in Canada. Quanta also acquired a pipeline services contractor located in the United States, the results of which are generally included in Quanta’s Oil and Gas Infrastructure Services segment. The aggregate consideration for these acquisitions consisted of $75.9 million paid or payable in cash, subject to certain adjustments, 70,840 shares of Quanta common stock valued at $1.5 million as of the settlement date of the applicable acquisition, and contingent consideration payments of up to $39.5 million , payable if financial targets are achieved by certain of the acquired businesses. Based on the estimated fair value of this contingent consideration, Quanta recorded a total of $18.7 million in liabilities as of the applicable acquisition dates. The results of the acquired businesses have been included in Quanta’s consolidated financial statements since the acquisition dates. 2015 Acquisitions During 2015, Quanta acquired 11 businesses. The results of eight of the acquired businesses are generally included in Quanta’s Electric Power Infrastructure Services segment. These businesses included a foundation services business located in the United States, an electrical contracting business located in the United States, an electrical engineering business located in Australia, a powerline construction business located in the United States, an engineering business located in Canada, an engineering, procurement and construction services business based in the United States, an underground construction contracting business located in Canada, and a supplier and material procurement specialist for the power and utility industry in Canada. The results of the remaining three acquired businesses are generally included in Quanta’s Oil and Gas Infrastructure Services segment. These businesses include a business that services above-ground storage tanks in the United States, an underground utility distribution contractor that provides services to gas and electric utilities in Canada, and a business that specializes in the engineering, procurement, construction, and commissioning of compression and surface facilities for the high pressure gas industry in Australia. The aggregate consideration for these acquisitions consisted of $110.6 million paid or payable in cash, subject to certain adjustments, 461,037 shares of Quanta common stock valued at $10.1 million as of the settlement dates of the applicable acquisitions, and contingent consideration payments with an estimated fair value of $1.0 million as of the applicable acquisition date. The results of the acquired businesses have been included in Quanta’s consolidated financial statements since the acquisition dates. 2017 , 2016 and 2015 Acquisitions The following table summarizes the aggregate consideration paid or payable as of December 31, 2017 for the 2017 and 2016 acquisitions and presents the allocation of these amounts to the net tangible and identifiable intangible assets based on their estimated fair values as of the respective acquisition dates, inclusive of any purchase price adjustments. This allocation requires a significant use of estimates and is based on information that was available to management at the time these consolidated financial statements were prepared. Quanta uses a variety of information to estimate fair values, including quoted market prices, carrying values and valuation techniques such as discounted cash flows. Third-party appraisal firms are engaged to assist in fair value determination of fixed assets, intangible assets and certain other assets and liabilities when appropriate (in thousands). 2017 2016 Stronghold Other Acquisitions All Acquisitions Consideration: Cash paid or payable $ 351,014 $ 11,904 $ 75,941 Value of Quanta common stock issued 81,337 8,267 1,508 Contingent consideration 51,084 — 18,683 Fair value of total consideration transferred or estimated to be transferred $ 483,435 $ 20,171 $ 96,132 Accounts receivable $ 77,478 $ 7,157 $ 14,414 Costs and estimated earnings in excess of billings on uncompleted contracts 11,913 193 1,237 Other current assets 20,914 170 8,582 Property and equipment 51,258 1,480 44,863 Other assets 1,513 12 2,553 Identifiable intangible assets 95,700 8,091 11,467 Current liabilities (71,835 ) (2,798 ) (12,097 ) Deferred tax liabilities, net — — (13,484 ) Other long-term liabilities (48 ) — (5,326 ) Total identifiable net assets 186,893 14,305 52,209 Goodwill 296,542 5,866 43,923 $ 483,435 $ 20,171 $ 96,132 Goodwill represents the excess of the purchase price over the net amount of the fair values assigned to assets acquired and liabilities assumed. The 2017 , 2016 and 2015 acquisitions strategically expanded Quanta’s Canadian, Australian and domestic electric power, oil and gas and communications service offerings, which Quanta believes contributes to the recognition of the goodwill. In connection with the 2017 acquisitions, as of the acquisition dates and inclusive of purchase price adjustments, goodwill of $5.9 million was recorded for the acquired businesses that were included within Quanta’s Electric Power Infrastructure Services Division, and goodwill of $296.5 million was recorded for Stronghold, which was included within Quanta’s Oil and Gas Infrastructure Services Division. In connection with the 2016 acquisitions, as of the acquisition dates and inclusive of purchase price adjustments, goodwill of $23.6 million was recorded for the acquired businesses included within Quanta’s Electric Power Infrastructure Services Division and goodwill of $20.3 million was recorded for the acquired business included within Quanta’s Oil and Gas Infrastructure Services Division. In connection with the 2015 acquisitions, as of the acquisition dates and inclusive of purchase price adjustments, goodwill of $31.5 million was recorded for acquired businesses that were included within Quanta’s Electric Power Infrastructure Services Division, and goodwill of $20.4 million was recorded for the acquired businesses that were included within Quanta’s Oil and Gas Infrastructure Services Division. Goodwill of $302.4 million related to the 2017 acquisitions is expected to be deductible for income tax purposes, and goodwill of $2.0 million related to the 2016 acquisitions is expected to be deductible for income tax purposes. The following table summarizes the estimated fair values of identifiable intangible assets for the 2017 acquisitions as of the acquisition dates and the related weighted average amortization periods by type (in thousands, except for weighted average amortization periods, which are in years). Estimated Weighted Average Fair Value Amortization Period in Years Customer relationships $ 76,213 6.8 Backlog 333 2.0 Trade names 18,815 15.0 Non-compete agreements 8,430 5.0 Total intangible assets subject to amortization acquired in 2017 acquisitions $ 103,791 8.1 The following unaudited supplemental pro forma results of operations have been provided for illustrative purposes only and do not purport to be indicative of the actual results that would have been achieved by the combined companies for the periods presented or that may be achieved by the combined companies in the future. Future results may vary significantly from the results reflected in the following pro forma financial information because of future events and transactions, as well as other factors (in thousands, except per share amounts): Year Ended December 31, 2017 2016 2015 Revenues $ 9,712,820 $ 8,183,104 $ 7,770,744 Gross profit $ 1,301,322 $ 1,129,661 $ 956,925 Selling, general and administrative expenses $ 821,084 $ 734,900 $ 612,979 Amortization of intangible assets $ 40,356 $ 46,579 $ 39,947 Net income from continuing operations $ 320,768 $ 207,956 $ 136,608 Net income from continuing operations attributable to common stock $ 317,521 $ 206,241 $ 125,691 Earnings per share from continuing operations: Basic $ 2.01 $ 1.29 $ 0.64 Diluted $ 2.00 $ 1.29 $ 0.64 The pro forma combined results of operations for the years ended December 31, 2017 and 2016 were prepared by adjusting the historical results of Quanta to include the historical results of the 2017 acquisitions as if they occurred January 1, 2016 . The pro forma combined results of operations for the year ended December 31, 2016 have also been prepared by adjusting the historical results of Quanta to include the historical results of the 2016 acquisitions as if they occurred January 1, 2015 . The pro forma combined results of operations for the year ended December 31, 2015 have been prepared by adjusting the historical results of Quanta to include the historical results of the 2016 acquisitions as if they occurred January 1, 2015 and the historical results of the 2015 acquisitions as if it occurred January 1, 2014 . These pro forma combined historical results were adjusted for the following: a reduction of interest expense as a result of the repayment of outstanding indebtedness of the acquired businesses; a reduction of interest income or an increase in interest expense as a result of the cash consideration paid net of cash received; an increase in amortization expense due to the incremental intangible assets recorded; changes in depreciation expense within cost of services to adjust acquired property and equipment to the acquisition date fair value and to conform with Quanta’s accounting policies; an increase in the number of outstanding shares of Quanta common stock; and reclassifications to conform the acquired companies’ presentation to Quanta’s accounting policies. The pro forma results of operations do not include any adjustments to eliminate the impact of acquisition related costs or any cost savings or other synergies that resulted or may result from the acquisitions. As noted above, the pro forma results of operations do not purport to be indicative of the actual results that would have been achieved by the combined company for the periods presented or that may be achieved by the combined company in the future. Revenues of approximately $207.4 million and a loss from continuing operations before income taxes of approximately $8.1 million , which included $5.4 million of acquisition-related costs, were included in Quanta’s consolidated results of operations for the year ended December 31, 2017 related to the 2017 acquisitions. Revenues of approximately $68.5 million and a loss from continuing operations before income taxes of approximately $5.6 million , which included $0.3 million of acquisition-related costs, were included in Quanta’s consolidated results of operations for the year ended December 31, 2016 related to the 2016 acquisitions. Additionally, revenues of approximately $104.6 million and income from continuing operations before income taxes of approximately $0.3 million , which included $3.6 million of acquisition-related costs, were included in Quanta’s consolidated results of operations for the year ended December 31, 2015 related to the 2015 acquisitions.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	GOODWILL AND OTHER INTANGIBLE ASSETS: A summary of changes in Quanta’s goodwill is as follows (in thousands): Electric Power Infrastructure Services Division Oil and Gas Infrastructure Services Division Total Balance at December 31, 2015: Goodwill $ 1,226,245 $ 366,306 1,592,551 Accumulated impairment — (39,893 ) (39,893 ) 1,226,245 326,413 1,552,658 Goodwill recorded related to 2016 acquisitions 24,168 21,018 45,186 Purchase price allocation adjustments 229 (214 ) 15 Foreign currency translation adjustments 3,337 1,973 5,310 Balance at December 31, 2016: Goodwill 1,253,979 388,923 1,642,902 Accumulated impairment — (39,733 ) (39,733 ) 1,253,979 349,190 1,603,169 Goodwill recorded related to 2017 acquisitions 5,866 296,542 302,408 Purchase price allocation adjustments (619 ) (659 ) (1,278 ) Goodwill impairment during 2017 — (57,011 ) (57,011 ) Foreign currency translation adjustments 13,301 8,011 21,312 Balance at December 31, 2017: Goodwill 1,272,527 693,905 1,966,432 Accumulated impairment — (97,832 ) (97,832 ) $ 1,272,527 $ 596,073 $ 1,868,600 Adjustments primarily represent changes in deferred tax liability estimates and would not have had a material impact on Quanta’s consolidated financial statements in prior periods had these adjustments been booked at the respective acquisition dates. The goodwill impairment in the year ended December 31, 2017 was associated with two reporting units within the Oil and Gas Infrastructure Services Division. Specifically, a reporting unit that provides material handling services experienced lower operating margins and is expected to continue to face a highly competitive environment in its select markets, and a reporting unit that provides marine and offshore services experienced prolonged periods of reduced revenues and operating margins and is expected to continue to experience lower levels of activity in the U.S. Gulf of Mexico and other offshore markets. Also, as described in Note 2, Quanta’s operating units are organized into one of Quanta’s two internal divisions and, accordingly, the goodwill associated with the operating units has been aggregated on a divisional basis in the table above. These divisions are closely aligned with Quanta’s reportable segments and operating units are assigned to a division based on the predominant type of work performed. From time to time, an operating unit may be reorganized between divisions if its predominant business evolves. Quanta’s intangible assets subject to amortization and the remaining weighted average amortization periods related to such assets were as follows (in thousands except for weighted average amortization periods, which are in years): As of As of As of December 31, 2017 December 31, 2016 December 31, 2017 Intangible Assets Accumulated Amortization Intangible Assets, Net Intangible Assets Accumulated Amortization Intangible Assets, Net Remaining Weighted Average Amortization Period in Years Customer relationships $ 327,334 $ (137,333 ) $ 190,001 $ 244,329 $ (110,640 ) $ 133,689 7.3 Backlog 136,266 (135,847 ) 419 133,592 (132,441 ) 1,151 1.1 Trade names 74,797 (17,057 ) 57,740 54,723 (12,855 ) 41,868 16.2 Non-compete agreements 37,760 (27,659 ) 10,101 29,212 (25,546 ) 3,666 3.9 Patented rights and developed technology 22,529 (17,611 ) 4,918 22,480 (15,831 ) 6,649 3.4 Total intangible assets subject to amortization $ 598,686 $ (335,507 ) $ 263,179 $ 484,336 $ (297,313 ) $ 187,023 9.1 Amortization expense for intangible assets was $32.2 million , $31.7 million and $34.8 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. During the year ended December 31, 2017, Quanta recorded an impairment charge of $1.1 million related to a customer relationships intangible asset, which primarily resulted from a strategic decision to restructure a business within a reporting unit in Quanta’s Oil and Gas Infrastructure Services Division. The impairment charge recognized in 2017 is reflected in the December 31, 2017 accumulated amortization balances above. Additionally, during the year ended December 31, 2015, Quanta recorded an impairment charge of $12.1 million related to customer relationship, trade name and non-compete agreement intangible assets. These intangible asset impairments primarily resulted from lower levels of expected activity in the U.S. Gulf of Mexico and, to a lesser extent, due to the extended low commodity price environment with respect to certain directional drilling operations in Australia. The two reporting units impacted are in Quanta’s Oil and Gas Infrastructure Services Division. The impairment charges recognized in 2015 are reflected in the December 31, 2017 and 2016 accumulated amortization balances above. The estimated future aggregate amortization expense of intangible assets subject to amortization as of December 31, 2017 is set forth below (in thousands): For the Fiscal Year Ending December 31, 2018 $ 39,188 2019 37,038 2020 35,639 2021 33,295 2022 29,764 Thereafter 88,255 Total $ 263,179

Per Share Information

Per Share Information	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Per Share Information	PER SHARE INFORMATION: The amounts used to compute the basic and diluted earnings per share attributable to common stock for the years ended December 31, 2017 , 2016 and 2015 are illustrated below (in thousands): Year Ended December 31, 2017 2016 2015 Amounts attributable to common stock: Net income from continuing operations $ 314,978 $ 198,725 $ 120,286 Net income (loss) from discontinued operations — (342 ) 190,621 Net income attributable to common stock $ 314,978 $ 198,383 $ 310,907 Weighted average shares: Weighted average shares outstanding for basic earnings per share attributable to common stock 156,124 157,287 195,113 Effect of dilutive unvested non-participating stock-based awards 1,031 1 7 Weighted average shares outstanding for diluted earnings per share attributable to common stock 157,155 157,288 195,120 For purposes of calculating diluted earnings per share attributable to common stock, there were no adjustments required to derive Quanta’s net income attributable to common stock. Exchangeable shares that were issued pursuant to certain of Quanta’s historical acquisitions (as further discussed in Note 11), which are exchangeable on a one -for-one basis with shares of Quanta common stock, have been included in the calculation of weighted average shares outstanding for basic and diluted earnings per share attributable to common stock for the portion of the periods that they were outstanding. Additionally, unvested stock-based awards that contain non-forfeitable rights to dividends or dividend equivalents (participating) have been included in the calculation of basic and diluted earnings per share attributable to common stock for the portion of the periods that they were outstanding. Diluted earnings per share attributable to common stock is computed using the weighted average number of common shares outstanding during the period adjusted for all potentially dilutive common stock equivalents, except in cases where the effect of the common stock equivalents would be antidilutive.

Detail of Certain Balance Sheet

Detail of Certain Balance Sheet Accounts	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Detail of Certain Balance Sheet Accounts	DETAIL OF CERTAIN BALANCE SHEET ACCOUNTS: Activity in Quanta’s current and long-term allowance for doubtful accounts consisted of the following (in thousands): December 31, 2017 2016 Balance at beginning of year $ 2,752 $ 5,226 Charged to bad debt expense (recoveries of bad debt expense) 87 (543 ) Deductions for uncollectible receivables written off (recoveries of uncollectible receivables) 1,626 (1,931 ) Balance at end of year $ 4,465 $ 2,752 Contracts in progress were as follows (in thousands): December 31, 2017 2016 Costs incurred on contracts in progress $ 7,912,999 $ 6,687,484 Estimated earnings, net of estimated losses 1,092,303 766,560 9,005,302 7,454,044 Less — Billings to date (8,941,397 ) (7,255,582 ) $ 63,905 $ 198,462 Costs and estimated earnings in excess of billings on uncompleted contracts $ 497,292 $ 473,308 Less — Billings in excess of costs and estimated earnings on uncompleted contracts (433,387 ) (274,846 ) $ 63,905 $ 198,462 Property and equipment consisted of the following (in thousands): Estimated Useful December 31, Lives in Years 2017 2016 Land N/A $ 48,832 $ 45,919 Buildings and leasehold improvements 5-30 155,628 137,515 Operating equipment and vehicles 5-25 1,834,715 1,634,850 Office equipment, furniture and fixtures and information technology systems 3-10 170,115 145,174 Construction work in progress N/A 60,587 73,461 2,269,877 2,036,919 Less — Accumulated depreciation and amortization (981,275 ) (862,825 ) Property and equipment, net $ 1,288,602 $ 1,174,094 Accounts payable and accrued expenses consisted of the following (in thousands): December 31, 2017 2016 Accounts payable, trade $ 632,931 $ 529,608 Accrued compensation and related expenses 225,193 194,056 Accrued insurance, current portion 64,112 60,880 Deferred revenues, current portion 15,967 15,512 Income and franchise taxes payable 19,635 40,765 Other accrued expenses 99,622 81,998 $ 1,057,460 $ 922,819

Debt Obligations

Debt Obligations	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt Obligations	DEBT OBLIGATIONS: Quanta’s long-term debt obligations consisted of the following (in thousands): December 31, 2017 2016 Borrowings under credit facility $ 668,427 $ 351,341 Other long-term debt, interest rates ranging from 2.4% to 4.3% 1,810 3,305 Capital leases, interest rates ranging from 2.5% to 3.8% 1,704 3,744 Total long-term debt obligations 671,941 358,390 Less — Current maturities of long-term debt 1,220 4,828 Total long-term debt obligations, net of current maturities $ 670,721 $ 353,562 Quanta’s current maturities of long-term debt and short-term debt consisted of the following (in thousands): December 31, 2017 2016 Short-term debt $ — $ 2,735 Current maturities of long-term debt 1,220 4,828 Current maturities of long-term debt and short-term debt $ 1,220 $ 7,563 Senior Secured Revolving Credit Facility On December 18, 2015, Quanta entered into an amended and restated credit agreement with various lenders that provides for a $1.81 billion senior secured revolving credit facility. On October 31, 2017, Quanta and the lenders entered into an amendment to the credit facility which, among other things, extended the maturity date from December 18, 2020 to October 31, 2022 and adjusted the interest rates applicable to certain borrowings. The entire amount available under the credit facility may be used by Quanta for revolving loans and letters of credit in U.S. dollars and certain alternative currencies. Up to $600.0 million of the credit facility may be used by certain subsidiaries of Quanta for revolving loans and letters of credit in certain alternative currencies. Up to $100.0 million of the credit facility may be used for swing line loans in U.S. dollars, up to $50.0 million of the credit facility may be used for swing line loans in Canadian dollars and up to $30.0 million of the credit facility may be used for swing line loans in Australian dollars. In addition, subject to the conditions specified in the credit agreement, Quanta has the option to increase the revolving commitments by up to $400.0 million from time to time upon receipt of additional commitments from new or existing lenders. Borrowings under the credit agreement are to be used to refinance existing indebtedness and for working capital, capital expenditures and other general corporate purposes. As of December 31, 2017 , Quanta had $413.3 million of outstanding letters of credit and bank guarantees under its senior secured revolving credit facility, $228.6 million of which were denominated in U.S. dollars and $184.7 million of which were denominated in currencies other than the U.S. dollar, primarily in Australian or Canadian dollars. Quanta also had $668.4 million of outstanding revolving loans under its credit facility, $645.0 million of which were denominated in U.S. dollars and $23.4 million of which were denominated in Australian dollars. The remaining $728.3 million was available for revolving loans or new letters of credit or bank guarantees. Borrowings under the credit facility and the applicable interest rates during the years ended December 31, 2017 , 2016 and 2015 were as follows (dollars in thousands): Year Ended December 31, 2017 2016 2015 Maximum amount outstanding under the credit facility during the period $ 917,895 $ 518,607 $ 606,753 Average daily amount outstanding under the credit facility $ 613,130 $ 458,908 $ 258,815 Weighted-average interest rate 2.7 % 2.1 % 1.8 % Beginning on November 20, 2017, amounts borrowed in U.S. dollars bear interest, at Quanta’s option, at a rate equal to either (i) the Eurocurrency Rate plus 1.125% to 2.000% , as determined based on Quanta’s Consolidated Leverage Ratio, or (ii) the Base Rate plus 0.125% to 1.000% , as determined based on Quanta’s Consolidated Leverage Ratio. Amounts borrowed as revolving loans under the credit agreement in any currency other than U.S. dollars bear interest at a rate equal to the Eurocurrency Rate plus 1.125% to 2.000% , as determined based on Quanta’s Consolidated Leverage Ratio. Additionally, standby or commercial letters of credit issued under the credit agreement are subject to a letter of credit fee of 1.125% to 2.000% , based on Quanta’s Consolidated Leverage Ratio, and Performance Letters of Credit issued under the credit agreement in support of certain contractual obligations are subject to a letter of credit fee of 0.675% to 1.150% , based on Quanta’s Consolidated Leverage Ratio. From December 18, 2015 through November 19, 2017, amounts borrowed in U.S. dollars bore interest, at Quanta’s option, at a rate equal to either (i) the Eurocurrency Rate (as defined in the credit agreement) plus 1.125% to 2.125% , as determined based on Quanta’s Consolidated Leverage Ratio (as described below), or (ii) the Base Rate (as described below) plus 0.125% to 1.125% , as determined based on Quanta’s Consolidated Leverage Ratio. Amounts borrowed as revolving loans under the credit agreement in any currency other than U.S. dollars bore interest at a rate equal to the Eurocurrency Rate plus 1.125% to 2.125% , as determined based on Quanta’s Consolidated Leverage Ratio. Standby letters of credit issued under the credit agreement were subject to a letter of credit fee of 1.125% to 2.125% , based on Quanta’s Consolidated Leverage Ratio, and Performance Letters of Credit (as defined in the credit agreement) issued under the credit agreement in support of certain contractual obligations were subject to a letter of credit fee of 0.675% to 1.275% , based on Quanta’s Consolidated Leverage Ratio. Quanta is also subject to a commitment fee of 0.20% to 0.40% , based on its Consolidated Leverage Ratio, on any unused availability under the credit agreement. The Consolidated Leverage Ratio is the ratio of Quanta’s Consolidated Funded Indebtedness to Consolidated EBITDA (as those terms are defined in the credit agreement). For purposes of calculating Quanta’s Consolidated Leverage Ratio, Consolidated Funded Indebtedness is reduced by available cash and cash equivalents (as defined in the credit agreement) in excess of $25.0 million . The Base Rate equals the highest of (i) the Federal Funds Rate (as defined in the credit agreement) plus 0.5% , (ii) the prime rate publicly announced by Bank of America, N.A. and (iii) the Eurocurrency Rate plus 1.00% . Subject to certain exceptions, the credit agreement is secured by substantially all the assets of Quanta and Quanta’s wholly owned U.S. subsidiaries and by a pledge of all of the capital stock of Quanta’s wholly owned U.S. subsidiaries and 65% of the capital stock of direct foreign subsidiaries of Quanta’s wholly owned U.S. subsidiaries. Quanta’s wholly owned U.S. subsidiaries also guarantee the repayment of all amounts due under the credit agreement. Subject to certain conditions, all collateral will automatically be released from the liens at any time Quanta maintains an Investment Grade Rating (defined in the credit agreement as two of the following three conditions being met: (i) a corporate credit rating that is BBB- or higher by Standard & Poor’s Rating Services, (ii) a corporate family rating that is Baa3 or higher by Moody’s Investors Services, Inc. or (iii) a corporate credit rating that is BBB- or higher by Fitch Ratings, Inc.). The credit agreement contains certain covenants, including (1) a maximum Consolidated Leverage Ratio of 3.0 to 1.0 (provided that in connection with certain permitted acquisitions in excess of $200.0 million , such ratio is 3.5 to 1.0 for the fiscal quarter in which the acquisition is completed and the two subsequent fiscal quarters) and (2) a minimum Consolidated Interest Coverage Ratio (as defined in the credit agreement) of 3.0 to 1.0. As of December 31, 2017 , Quanta was in compliance with all of the covenants in the credit agreement. The credit agreement also limits certain acquisitions, mergers and consolidations, indebtedness, asset sales and prepayments of indebtedness and, subject to certain exceptions, prohibits liens on Quanta’s assets. The credit agreement allows cash payments for dividends and stock repurchases subject to compliance with the following requirements (after giving effect to the dividend or stock repurchase): (i) no default or event of default under the credit agreement; (ii) continued compliance with the financial covenants in the credit agreement; and (iii) at least $100.0 million of availability under the credit agreement and/or cash and cash equivalents on hand. The credit agreement provides for customary events of default and contains cross-default provisions with Quanta’s underwriting, continuing indemnity and security agreement with its sureties and all of Quanta’s other debt instruments exceeding $100.0 million in borrowings or availability. If an Event of Default (as defined in the credit agreement) occurs and is continuing, on the terms and subject to the conditions set forth in the credit agreement, the lenders may declare all amounts outstanding and accrued and unpaid interest immediately due and payable, require that Quanta provide cash collateral for all outstanding letter of credit obligations, terminate the commitments under the credit agreement, and foreclose on the collateral. Prior to the amendment and restatement of Quanta’s credit agreement on December 18, 2015 and after April 1, 2014, amounts borrowed bore interest at the same rates as the period from December 18, 2015 through November 19, 2017 described above, and Quanta was subject to the same commitment fees as above. Other Facilities Quanta has also entered into bilateral credit agreements with various lenders that provide for up to $50.2 million in aggregate availability in both U.S. dollars and certain alternative currencies, primarily Australian dollars. Quanta may utilize these facilities for, among other things, the issuance of letters of credit or bank guarantees and overdraft protection and had $2.8 million of letters of credit and bank guarantees outstanding under these facilities at December 31, 2017 .

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES: The Tax Act, among other things, lowers the U.S. corporate income tax rate from 35% to 21% effective January 1, 2018, requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries, limits and eliminates certain tax deductions and creates new taxes on certain foreign-sourced earnings. Consequently, during the year ended December 31, 2017, one-time net tax benefits of $70.1 million were recorded, including $85.3 million of tax benefits associated with the re-measurement of U.S. deferred tax assets and liabilities based on rates at which they are expected to reverse in future periods, which is generally 21%; partially offset by an estimated $15.2 million transition tax on post-1986 earnings and profits of certain foreign subsidiaries. Also during the year ended December 31, 2017, an additional one-time tax benefit of $26.7 million was recorded associated with entity restructuring and recapitalization efforts, partially offset by an $8.5 million decrease of the production activity related tax benefit due to the acceleration of certain deductions in 2017. While Quanta has substantially completed its provisional analysis of the effects of the Tax Act and recorded a reasonable estimate of such effects, the net one-time benefits related to the Tax Act may differ, possibly materially, due to, among other things, further refinement of Quanta’s calculations, changes in interpretations and assumptions made, additional regulatory guidance, and actions and related accounting policy decisions resulting from the Tax Act. Quanta will complete its analysis over a one-year measurement period ending December 22, 2018, and any adjustments during the measurement period will be included within “Net income from continuing operations” as an adjustment to “Provision for income taxes” on Quanta’s consolidated statement of operations in the reporting period when such adjustments are determined. The components of income (loss) from continuing operations before income taxes were as follows (in thousands): Year Ended December 31, 2017 2016 2015 Income (loss) from continuing operations before income taxes: Domestic $ 291,031 $ 349,959 $ 244,955 Foreign 62,726 (42,273 ) (16,280 ) Total $ 353,757 $ 307,686 $ 228,675 The components of the provision for income taxes for continuing operations were as follows (in thousands): Year Ended December 31, 2017 2016 2015 Current: Federal $ 44,695 $ 106,316 $ 85,830 State 301 11,549 9,783 Foreign 22,666 5,076 21,262 Total current tax provision 67,662 122,941 116,875 Deferred: Federal (36,915 ) (264 ) (5,247 ) State 14,951 (923 ) 917 Foreign (10,166 ) (14,508 ) (15,073 ) Total deferred tax benefit (32,130 ) (15,695 ) (19,403 ) Total provision for income taxes from continuing operations $ 35,532 $ 107,246 $ 97,472 The actual income tax provision differed from the income tax provision computed by applying the U.S. federal statutory corporate rate to income from continuing operations before provision for income taxes as follows (in thousands): Year Ended December 31, 2017 2016 2015 Provision at the statutory rate $ 123,815 $ 107,690 $ 80,036 Increases (decreases) resulting from — Tax Cuts and Jobs Act (70,129 ) — — State taxes 17,920 6,479 7,241 Foreign taxes (16,958 ) 1,860 1,239 Contingency reserves, net 3,651 (13,540 ) 4,438 Production activity deduction (1,504 ) (8,586 ) (6,871 ) Employee per diems, meals and entertainment 13,605 8,764 8,727 Taxes on unincorporated joint ventures (1,354 ) (656 ) (3,838 ) Asset impairments — 1,909 7,047 Entity restructuring and recapitalization efforts (26,668 ) — — Equity compensation (5,095 ) — — Other (1,751 ) 3,326 (547 ) Total provision for income taxes from continuing operations $ 35,532 $ 107,246 $ 97,472 Deferred income taxes result from temporary differences in the recognition of income and expenses for financial reporting purposes and tax purposes. The tax effects of these temporary differences, representing deferred tax assets and liabilities, result principally from the following (in thousands): December 31, 2017 2016 Deferred income tax liabilities: Property and equipment $ (161,491 ) $ (214,902 ) Goodwill (49,407 ) (83,097 ) Other intangibles (26,676 ) (33,566 ) Customer holdbacks (36,218 ) (16,424 ) Other book/tax accounting method differences (15,154 ) (24,817 ) Total deferred income tax liabilities (288,946 ) (372,806 ) Deferred income tax assets: Accruals and reserves 21,419 21,681 Accrued insurance — 79,630 Stock and incentive compensation and pension withdrawal liabilities 17,676 58,744 Net operating loss carryforwards 62,925 37,362 Tax credits 48,516 1,613 Other 4,747 5,933 Subtotal 155,283 204,963 Valuation allowance (19,328 ) (14,991 ) Total deferred income tax assets 135,955 189,972 Total net deferred income tax liabilities $ (152,991 ) $ (182,834 ) The net deferred income tax assets and liabilities were comprised of the following in the accompanying consolidated balance sheets (in thousands): December 31, 2017 2016 Deferred income taxes: Assets $ 26,390 $ 10,000 Liabilities (179,381 ) (192,834 ) Total net deferred income tax liabilities $ (152,991 ) $ (182,834 ) The valuation allowance for deferred income tax assets at December 31, 2017 , 2016 and 2015 was $19.3 million , $15.0 million and $16.1 million , respectively. These valuation allowances relate to state and foreign net operating loss carryforwards. The net change in the total valuation allowance for each of the years ended December 31, 2017 , 2016 and 2015 was an increase of $4.3 million , a decrease of $1.1 million and an increase of $3.1 million , respectively. The valuation allowance was established primarily as a result of uncertainty in Quanta’s outlook as to future taxable income in particular tax jurisdictions. Quanta believes it is more likely than not that it will realize the benefit of its deferred tax assets net of existing valuation allowances. At December 31, 2017 , Quanta had state and foreign net operating loss carryforwards, the tax effect of which was $67.9 million . These carryforwards will expire as follows: 2018 , $0.2 million ; 2019 , $0.1 million ; 2020 , $1.9 million ; 2021 , $0.1 million ; 2022 , $0.2 million and $65.4 million thereafter. A valuation allowance of $17.8 million has been recorded against certain foreign and state net operating loss carryforwards. Quanta generally does not provide for taxes related to undistributed earnings of its foreign subsidiaries because such earnings either would not be taxable when remitted or they are considered to be indefinitely reinvested. Quanta could also be subject to additional foreign withholding taxes if it were to repatriate cash that is indefinitely reinvested outside the United States, but it does not expect such amount to be material. A reconciliation of unrecognized tax benefit balances is as follows (in thousands): December 31, 2017 2016 2015 Balance at beginning of year $ 35,240 $ 54,541 $ 50,668 Additions based on tax positions related to the current year 7,040 4,227 5,340 Additions for tax positions of prior years 3,372 2,048 292 Reductions for tax positions of prior years (1,171 ) (1,948 ) (132 ) Reductions for audit settlements — (180 ) (1,345 ) Reductions resulting from a lapse of the applicable statute of limitations periods (8,252 ) (23,448 ) (282 ) Balance at end of year $ 36,229 $ 35,240 $ 54,541 For the year ended December 31, 2017 , the $8.3 million reduction was primarily due to the expiration of certain federal and state statute of limitations periods for the 2013 tax year. For the year ended December 31, 2016 , the $23.4 million reduction was primarily due to the expiration of certain federal and state statute of limitations periods for the 2010 through 2012 tax years. For the year ended December 31, 2015 , the $0.3 million reduction was primarily due to the expiration of certain federal and state statute of limitations periods for the 2004 tax year. The balances of unrecognized tax benefits, the amount of related interest and penalties and what Quanta believes to be the range of reasonably possible changes in the next 12 months are as follows (in thousands): December 31, 2017 2016 2015 Unrecognized tax benefits $ 36,229 $ 35,240 $ 54,541 Portion that, if recognized, would reduce tax expense and effective tax rate 35,561 33,128 48,312 Accrued interest on unrecognized tax benefits 5,368 5,539 8,750 Accrued penalties on unrecognized tax benefits 631 650 673 Reasonably possible reduction to the balance of unrecognized tax benefits in succeeding 12 months $0 to $13,655 $0 to $12,332 $0 to $27,485 Portion that, if recognized, would reduce tax expense and effective tax rate $0 to $12,483 $0 to $10,983 $0 to $24,009 Quanta classifies interest and penalties within the provision for income taxes. Quanta recognized interest income of $0.2 million , interest income of $3.2 million and interest expense of $2.4 million in the provision for income taxes for the years ended December 31, 2017 , 2016 and 2015 , respectively. Although the IRS completed its examination related to tax years 2010, 2011 and 2012 during 2016, certain subsidiaries remain under examination by various U.S. state, Canadian and other foreign tax authorities for multiple periods. Quanta’s Canadian subsidiaries remain open to examination by the Canada Revenue Agency for tax years 2010 through 2014 as these statute of limitations periods have not yet expired. Quanta does not consider any state in which it does business to be a major tax jurisdiction.

Equity

Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Equity	EQUITY: Exchangeable Shares and Series F and Series G Preferred Stock In connection with certain Canadian acquisitions, the former owners of the acquired companies received exchangeable shares of certain Canadian subsidiaries of Quanta, which may be exchanged at the option of the holders for Quanta common stock on a one -for-one basis. The holders of exchangeable shares can make an exchange only once in any calendar quarter and must exchange a minimum of either 50,000 shares or, if less, the total number of remaining exchangeable shares registered in the name of the holder making the request. Additionally, in connection with two of such acquisitions, Quanta issued one share of Quanta Series F preferred stock and one share of Quanta Series G preferred stock to voting trusts on behalf of the respective holders of the exchangeable shares issued in such acquisitions. The one share of Quanta Series F preferred stock was subsequently redeemed and retired effective October 6, 2017. The share of Quanta Series G preferred stock provides the holder of such exchangeable shares voting rights in Quanta common stock equivalent to the number of exchangeable shares outstanding. The holder of exchangeable shares associated with the Quanta Series G preferred stock has rights equivalent to Quanta common stockholders with respect to voting, dividends and other economic rights. The holders of exchangeable shares not associated with the Quanta Series G preferred stock have rights equivalent to Quanta common stockholders with respect to dividends and other economic rights but do not have voting rights. During 2017 , 2016 and 2015 , 6.0 million , 0.4 million and 0.4 million exchangeable shares were exchanged for Quanta common stock. As of December 31, 2017 , the Quanta Series G preferred stock remained outstanding and 0.5 million exchangeable shares remained outstanding, of which 0.4 million were associated with the Quanta Series G preferred stock. Treasury Stock General Treasury stock is recorded at cost. Under Delaware corporate law, treasury stock is not counted for quorum purposes or entitled to vote. Shares withheld for tax withholding obligations Under the stock incentive plans described in Note 12, the tax withholding obligations of employees upon vesting of restricted stock, RSUs and performance units settled in common stock are typically satisfied by Quanta making such tax payments and withholding the number of vested shares having a value on the date of vesting equal to the tax withholding obligation. For the settlement of these employee tax liabilities, Quanta withheld 0.5 million shares of Quanta common stock during the year ended December 31, 2017 , with a total market value of $18.6 million , 0.4 million shares of Quanta common stock during the year ended December 31, 2016 with a total market value of $8.3 million , and 0.4 million shares of Quanta common stock during the year ended December 31, 2015 with a total market value of $10.4 million . These shares and the related costs to acquire them were accounted for as adjustments to the balance of treasury stock. Notional amounts recorded related to deferred compensation plans For RSUs and performance units that vest but the settlement of which is deferred under Quanta’s deferred compensation plans, Quanta records an amount to treasury stock and an offsetting amount to APIC. No shares are recorded as treasury stock at vesting as the shares of Quanta common stock associated with deferred equity awards are not issued. Upon settlement of the deferred equity awards and issuance of the associated Quanta common stock, the original accounting entry is reversed. The net amounts recorded to treasury stock related to the deferred compensation plans during the years ended December 31, 2017 , 2016 and 2015 were $2.6 million , $6.8 million and $6.6 million , respectively. An aggregate $16.9 million was included in treasury stock for notional amounts related to deferred compensation plans at December 31, 2017 . Retirement of Treasury Stock Effective December 1, 2016 , Quanta retired 84.8 million shares of treasury stock. These retired shares were restored to the status of authorized and unissued shares as permitted by Delaware law. The retired stock had a carrying amount of $1.95 billion . In accordance with Quanta’s policy, Quanta recorded the formal retirement of treasury stock by deducting the par value from common stock and the excess of cost over par value from APIC. Stock repurchases During the second quarter of 2017, Quanta’s board of directors approved a stock repurchase program that authorizes Quanta to purchase, from time to time through June 30, 2020, up to $300.0 million of its outstanding common stock (the 2017 Repurchase Program). Repurchases under the 2017 Repurchase Program can be made in open market and privately negotiated transactions. As of December 31, 2017 , Quanta had repurchased 1.4 million shares of its common stock at a cost of $50.0 million in the open market under the 2017 Repurchase Program. During the third quarter of 2015, Quanta’s board of directors approved a stock repurchase program that authorized Quanta to purchase, from time to time through February 28, 2017, up to $1.25 billion of its outstanding common stock (the 2015 Repurchase Program). During 2015, Quanta repurchased 19.2 million shares of its common stock at a cost of $449.9 million in the open market under the 2015 Repurchase Program. During the third quarter of 2015, Quanta also entered into an accelerated share repurchase arrangement (the ASR) to repurchase $750.0 million of its common stock under the 2015 Repurchase Program. Pursuant to the terms of the ASR, based on the final volume-weighted average share price during the term of the ASR, minus a discount and subject to other adjustments, Quanta paid $750.0 million to JPMorgan Chase Bank, National Association, London Branch (JPMorgan) and received 25.7 million shares of its common stock in the third quarter of 2015 and 9.4 million shares of its common stock in the second quarter of 2016. As a result, Quanta repurchased a total of 54.3 million shares of its common stock at a cost of $1.20 billion under the 2015 Repurchase Program prior to its termination on February 28, 2017. During the fourth quarter of 2013, Quanta’s board of directors approved a stock repurchase program authorizing Quanta to purchase, from time to time through December 31, 2016, up to $500 million of its outstanding common stock (the 2013 Repurchase Program). During the year ended December 31, 2015, Quanta repurchased 14.3 million shares of its common stock at a cost of $406.5 million in the open market and completed the 2013 Repurchase Program. Non-controlling Interests Quanta holds investments in several joint ventures that provide infrastructure services under specific customer contracts. Quanta has determined that certain of these joint ventures are VIEs, with Quanta providing the majority of the infrastructure services to the joint venture, which management believes most significantly influences the economic performance of the joint venture. Management has concluded that Quanta is the primary beneficiary of each of the joint ventures determined to be VIEs and has accounted for each on a consolidated basis. The other parties’ equity interests in these joint ventures have been accounted for as “Non-controlling interests” in Quanta’s consolidated balance sheets. Net income attributable to the other joint venture members in the amounts of $3.2 million , $1.7 million and $10.9 million for the years ended December 31, 2017 , 2016 and 2015 , respectively, has been accounted for as a reduction of net income in deriving “Net income attributable to common stock” in Quanta’s consolidated statements of operations. The carrying amount of the investments held by Quanta in all of its VIEs was $7.8 million and $3.3 million at December 31, 2017 and 2016 . The carrying amount of investments held by the non-controlling interests in these VIEs at December 31, 2017 and 2016 was $4.1 million and $3.3 million . During the years ended December 31, 2017 , 2016 and 2015 , net distributions to non-controlling interests were $2.0 million , $0.8 million and $18.9 million . There were also a discharge of a note receivable from a joint venture partner of $0.5 million , which was accounted for as a “Buyout of a non-controlling interest” in the accompanying consolidated statement of equity for the year ended December 31, 2017. There were no other changes in equity as a result of transfers to/from the non-controlling interests during the years ended December 31, 2017 , 2016 and 2015 . See Note 15 for further disclosures related to Quanta’s joint venture arrangements.

Equity-Based Compensation

Equity-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity-Based Compensation	EQUITY-BASED COMPENSATION: Stock Incentive Plans On May 19, 2011, Quanta’s stockholders approved the 2011 Omnibus Equity Incentive Plan (the 2011 Plan). The 2011 Plan provides for the award of non-qualified stock options, incentive (qualified) stock options, stock appreciation rights, restricted stock, RSUs, stock bonus awards, performance compensation awards (including performance units and cash bonus awards) or any combination of the foregoing. The purpose of the 2011 Plan is to attract and retain key personnel and provide participants with additional performance incentives by increasing their proprietary interest in Quanta. Employees, directors, officers, consultants or advisors of Quanta or its affiliates are eligible to participate in the 2011 Plan, as are prospective employees, directors, officers, consultants or advisors of Quanta who have agreed to serve Quanta in those capacities. An aggregate of 11,750,000 shares of Quanta common stock may be issued pursuant to awards granted under the 2011 Plan. Quanta also has a Restricted Stock Unit Plan (the RSU Plan), pursuant to which RSUs may be awarded to certain employees and consultants of Quanta’s Canadian operations. The 2011 Plan and the RSU Plan are referred to as the Plans. The Plans are administered by the Compensation Committee of the Board of Directors of Quanta. The Compensation Committee has, subject to applicable regulation and the terms of the Plans, the authority to grant awards under the Plans, to construe and interpret the Plans and to make all other determinations and take any and all actions necessary or advisable for the administration of the Plans. The Board also delegated to the Equity Grant Committee, a committee of the Board consisting of one or more directors, the authority to grant limited awards to eligible persons who are not executive officers or non-employee directors. Restricted Stock and RSUs to be Settled in Common Stock During the years ended December 31, 2017 , 2016 and 2015 , Quanta granted 1.5 million , 1.8 million and 1.3 million shares of RSUs to be settled in common stock under the 2011 Plan with weighted average grant date fair values of $37.06 , $22.22 and $27.64 per share, respectively. The grant date fair value for RSUs to be settled in common stock is based on the market value of Quanta common stock on the date of grant. RSU awards to be settled in common stock are subject to forfeiture, restrictions on transfer and certain other conditions until vesting, which generally occurs in equal installments over a two -year, three -year or five -year period following the date of grant. Holders of RSUs to be settled in common stock are entitled to receive a cash dividend equivalent payment equal to any cash dividend payable on account of common shares. During the years ended December 31, 2017 , 2016 and 2015 , vesting activity consisted of 1.5 million , 1.4 million and 1.3 million shares of restricted stock and RSUs settled in common stock with an approximate fair value at the time of vesting of $55.6 million , $28.9 million and $35.9 million , respectively. As of December 31, 2017 , there was no restricted stock outstanding. A summary of the activity for RSUs to be settled in common stock for the year ended December 31, 2017 is as follows (shares in thousands): Shares Weighted Average Grant Date Fair Value (Per share) Unvested at December 31, 2016 2,711 $25.45 Granted 1,459 $37.06 Vested (1,489 ) $28.03 Forfeited (81 ) $27.58 Unvested at December 31, 2017 2,600 $30.42 During the years ended December 31, 2017 , 2016 and 2015 , Quanta recognized $41.0 million , $39.6 million and $33.3 million of non-cash stock compensation expense related to restricted stock and RSUs to be settled in common stock. As of December 31, 2017 , there was $38.2 million of total unrecognized compensation cost related to unvested RSUs to be settled in common stock granted to both employees and non-employees. This cost is expected to be recognized over a weighted average period of 1.61 years . Performance Units to be Settled in Common Stock Performance units awarded pursuant to the 2011 Plan provide for the issuance of shares of common stock upon vesting. These performance units cliff-vest at the end of a three -year performance period based on achievement of certain performance metrics established by Quanta’s compensation committee, including company performance goals and, with respect to certain awards, Quanta’s total shareholder return as compared to a predetermined group of peer companies. The final number of earned and vested performance units can range from 0% to 200% of the initial award based on the level of achievement, as determined by Quanta’s compensation committee. During the years ended December 31, 2017 , 2016 and 2015 , Quanta granted 0.3 million , 0.3 million and 0.2 million of performance units to be settled in common stock under the 2011 Plan with a weighted average grant date fair value of $17.63 , $22.86 and $28.16 per unit. The grant date fair value for awards of performance units without market-based metrics was based on the market value of Quanta common stock on the date of grant applied to the total number of performance units that Quanta anticipates will vest. The grant date fair value for awards of performance units with market-based metrics, which were granted in the year ended December 31, 2017 , was based on a fair value as determined using a Monte Carlo simulation valuation methodology using the following key inputs: Valuation date stock price based on the March 22, 2017 closing stock price $36.31 Expected volatility 36.00 % Risk-free interest rate 1.46 % Term in years 2.78 This fair value is expensed ratably over the three -year performance period and is adjusted for changes in the expected probability of achievement of the underlying goals and the resulting number of performance units anticipated to vest, so that the expense recognized is equivalent to the proportion of the three -year period that has expired, multiplied by the fair value of the number of performance units anticipated to vest. During the years ended December 31, 2017 , 2016 and 2015 , Quanta recognized $5.4 million , $3.2 million and $3.6 million in compensation expense associated with performance units. During the year ended December 31, 2017 , 0.1 million performance units vested, and 0.1 million shares of common stock were issued in connection with performance units. During the years ended December 31, 2016 and 2015 , no performance units vested, and no shares of common stock were issued in connection with performance units. RSUs to be Settled in Cash Certain RSUs granted by Quanta under the Plans are settled solely in cash. These cash-settled RSUs are intended to provide plan participants with cash performance incentives that are substantially equivalent to the risks and rewards of equity ownership in Quanta, typically vest in equal installments over a two -year or three -year period following the date of grant, and are subject to forfeiture under certain conditions, primarily termination of service. Additionally, subject to certain restrictions, Quanta’s non-employee directors may elect to cash settle a portion of their RSU awards, which generally vest upon conclusion of the director service year. For RSUs settled in cash, the holders receive for each vested RSU an amount in cash equal to the fair market value of one share of Quanta common stock on the settlement date, as specified in the applicable award agreement. Compensation expense related to RSUs to be settled in cash was $8.1 million , $7.0 million and $4.0 million for the years ended December 31, 2017 , 2016 and 2015 . Such expense is recorded in selling, general and administrative expenses. RSUs that are anticipated to be settled in cash are not included in the calculation of earnings per share, and the estimated earned value of such RSUs is classified as a liability. Quanta paid $8.6 million , $4.6 million and $4.2 million to settle liabilities related to cash-settled RSUs in the years ended December 31, 2017 , 2016 and 2015 , respectively. Accrued liabilities for the estimated earned value of outstanding RSUs to be settled in cash were $4.6 million and $5.1 million at December 31, 2017 and 2016 .

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefit Plans	EMPLOYEE BENEFIT PLANS: Unions’ Multiemployer Pension Plans Quanta contributes to a number of multiemployer defined benefit pension plans under the terms of collective bargaining agreements with various unions that represent certain of Quanta’s employees. Quanta’s multiemployer pension plan contribution rates generally are specified in the collective bargaining agreements (usually on an annual basis), and contributions are made to the plans on a “pay-as-you-go” basis based on its union employee payrolls. Quanta may also have additional liabilities imposed by law as a result of its participation in multiemployer defined benefit pension plans. The Employee Retirement Income Security Act of 1974, as amended by the Multiemployer Pension Plan Amendments Act of 1980, imposes certain liabilities upon an employer who is a contributor to a multiemployer pension plan if the employer withdraws from the plan or the plan is terminated or experiences a mass withdrawal. In the fourth quarter of 2011, Quanta recorded a partial withdrawal liability related to the withdrawal by certain Quanta subsidiaries from the Central States, Southeast and Southwest Areas Pension Plan (Central States Plan) following an amendment to the applicable collective bargaining agreement which eliminated their obligations to contribute to the Central States Plan. During the first quarter of 2014, Quanta recorded an adjustment to cost of services to increase the recognized withdrawal liability. Additional information regarding this withdrawal, as well as the withdrawal from the Central States Plan of a company acquired by Quanta in the fourth quarter of 2013, is provided in Collective Bargaining Agreements in Note 15. The Pension Protection Act of 2006 (PPA) also added special funding and operational rules generally applicable to plan years beginning after 2007 for multiemployer plans in the United States that are classified as “endangered,” “seriously endangered” or “critical” status based on multiple factors (including, for example, the plan’s funded percentage, cash flow position and whether it is projected to experience a minimum funding deficiency). Plans in these classifications must adopt measures to improve their funded status through a funding improvement or rehabilitation plan, as applicable, which may require additional contributions from employers (which may take the form of a surcharge on benefit contributions) and/or modifications to retiree benefits. Certain plans to which Quanta contributes or may contribute in the future are in “endangered,” “seriously endangered” or “critical” status. The amount of additional funds, if any, that Quanta may be obligated to contribute to these plans in the future cannot be estimated due to uncertainty of the future levels of work that require the specific use of union employees covered by these plans, as well as the future contribution levels and possible surcharges on contributions applicable to these plans. The following table summarizes plan information relating to Quanta’s participation in multiemployer defined benefit pension plans, including company contributions for the last three years, the status under the PPA of the plans and whether the plans are subject to a funding improvement or rehabilitation plan or contribution surcharges. The most recent PPA zone status available in 2017 and 2016 relates to the plan’s fiscal year-end in 2016 and 2015 . Forms 5500 were not yet available for the plan years ending in 2017 . The PPA zone status is based on information that Quanta received from the respective plans, as well as publicly available information on the U.S. Department of Labor website, and is certified by the plan’s actuary. Although multiple factors or tests may result in red zone or yellow zone status, plans in the red zone generally are less than 65 percent funded, plans in the yellow zone generally are less than 80 percent funded, and plans in the green zone generally are at least 80 percent funded. Under the PPA, red zone plans are classified as “critical” status, yellow zone plans are classified as “endangered” status and green zone plans are classified as neither “endangered” nor “critical” status. The “Subject to Financial Improvement/ Rehabilitation Plan” column indicates plans for which a financial improvement plan or a rehabilitation plan is either pending or has been implemented. The last column lists the expiration dates of Quanta’s collective-bargaining agreements to which the plans are subject. Total contributions to these plans correspond to the number of union employees employed at any given time and the plans in which they participate and vary depending upon the location and number of ongoing projects at a given time and the need for union resources in connection with such projects. Information has been presented separately for individually significant plans, based on PPA funding status classification, and in the aggregate for all other plans. Employee Identification Number/ Pension Plan Number PPA Zone Status Subject to Financial Improve- ment/ Reha- bilitation Plan Contributions (in thousands) Sur-charge Imposed Expiration Date of Collective Bargaining Agreement Fund 2017 2016 2017 2016 2015 National Electrical Benefit Fund 53-0181657-001 Green Green No $ 29,161 $ 22,912 $ 21,200 No Varies through May 2022 Pipeline Industry Pension Fund 73-6146433-001 Green Green No 13,585 6,954 6,087 No Varies through May 2020 Central Pension Fund of the IUOE & Participating Employers 36-6052390-001 Green Green No 12,176 5,668 5,677 No Varies through December 2020 Teamsters National Pipe Line Pension Plan 46-1102851-001 Green Green No 3,602 1,661 1,343 No Varies through December 2020 Laborers Pension Trust Fund for Northern California 94-6277608-001 Yellow Yellow Yes 3,387 3,805 2,603 Yes Varies through May 2020 Eighth District Electrical Pension Fund 84-6100393-001 Green Green No 3,208 3,089 2,544 No Varies through December 2020 Laborers National Pension Fund 75-1280827-001 Green Green No 3,049 1,358 7,671 No Varies through December 2020 Alaska Electrical Pension Plan 92-6005171-001 Green Green No 2,143 2,701 639 No Varies through December 2019 Operating Engineers Local 324 Pension Fund 38-1900637-001 Red Red Yes 1,969 1,291 1,231 Yes Varies through December 2020 OE Pension Trust Fund 94-6090764-001 Red Red Yes 1,703 1,508 1,264 Yes Varies through June 2020 Plumbers and Pipefitters National Pension Fund 52-6152779-001 Yellow Yellow Yes 1,273 1,666 850 No Varies through March 2021 Alaska Laborers - Employers Retirement Fund 91-6028298-001 Yellow Yellow Yes 536 1,216 181 No December 2018 Laborers District Council of W PA Pension Fund 25-6135576-001 Red Red Yes 418 876 21 Yes May 2018 Alaska Teamster Employer Pension Plan 92-6003463-024 Red Red Yes 255 659 513 Yes December 2018 Midwest Operating Engineers Pension Trust Fund 36-6140097-001 Yellow Yellow Yes 106 793 3,294 Yes June 2019 All other plans - U.S. 24,234 28,516 20,594 All other plans - Canada (1) 9,277 562 1,303 Total $ 110,082 $ 85,235 $ 77,015 (1) Multiemployer defined benefit pension plans in Canada are not subject to the reporting requirements under the PPA. Accordingly, certain information was not publicly available. Quanta’s contributions to the following individually significant plans were five percent or more of the total contributions to these plans for the periods indicated based on the Forms 5500 for these plans for the years ended December 31, 2016 and 2015 . Forms 5500 were not yet available for these plans for the year ended December 31, 2017 . Pension Fund Plan Years in which Quanta Contributions Were Five Percent or More of Total Plan Contributions Pipeline Industry Pension Fund 2016 and 2015 Eighth District Electrical Pension Fund 2016 and 2015 Local 697 IBEW and Electrical Industry Pension Fund 2016 and 2015 Local Union No. 9 IBEW and Outside Contractors Pension Fund 2016 and 2015 Alaska Plumbing and Pipefitting Industry Pension Fund 2016 and 2015 Teamsters National Pipe Line Pension Plan 2016 and 2015 Alaska Electrical Pension Plan 2016 IBEW Local 456 Pension Plan 2016 Michigan Electrical Employees’ Pension Plan 2016 Laborers National Pension Fund 2015 Michigan Upper Peninsula Intrl Brotherhood of Elec Workers Pension Plan 2015 In addition to the contributions made to multiemployer defined benefit pension plans noted above, Quanta also contributed to multiemployer defined contribution or other benefit plans on behalf of certain union employees. Contributions to union multiemployer defined contribution or other benefit plans by Quanta were $171.4 million , $139.3 million and $147.1 million for the years ended December 31, 2017 , 2016 and 2015 . Total contributions made to all of these multiemployer plans for the years ended December 31, 2017 , 2016 and 2015 correspond to the number of union employees employed at any given time and the plans in which they participate and vary depending upon the location and number of ongoing projects at a given time and the need for union resources in connection with such projects. Quanta 401(k) Plan Quanta maintains a 401(k) plan pursuant to which employees who are not provided retirement benefits through a collective bargaining agreement may make contributions through a payroll deduction. Quanta makes matching cash contributions of 100% of each employee’s contribution up to 3% of that employee’s salary and 50% of each employee’s contribution between 3% and 6% of such employee’s salary, up to the maximum amount permitted by law. Contributions to the 401(k) plan by Quanta were $26.3 million , $21.9 million and $17.7 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Deferred Compensation Plans Quanta maintains nonqualified deferred compensation plans pursuant to which non-employee directors and certain key employees, independent contractors and consultants may defer receipt of some or all of their cash compensation and/or settlement of their equity-based awards, subject to certain limitations. The plan covering key employees provides for employer matching contributions for certain officers and employees whose benefits under the 401(k) plan are limited by federal tax law. Quanta may also make discretionary employer contributions to that plan. Matching contributions and discretionary employer contributions are subject to a vesting schedule, provided that vesting accelerates upon a change in control and the participant’s death or retirement. All matching and discretionary employer contributions, whether vested or not, are forfeited upon a participant’s termination of employment for cause or upon the participant engaging in competition with Quanta or any of its affiliates. Quanta made contributions to the deferred compensation plans of $1.1 million , $1.0 million and $1.0 million during the years ended December 31, 2017 , 2016 and 2015 , respectively. At December 31, 2017 and 2016 , obligations under these plans were $30.1 million and $19.1 million and were included in “Insurance and other non-current liabilities” in the accompanying consolidated balance sheets, and investments in company-owned life insurance policies of $28.7 million and $17.9 million were included in “Other assets, net” in the accompanying consolidated balance sheets. Individuals participating in these plans receive distributions of their respective balances based on predetermined payout schedules or other events and are also able to direct investments made on their behalf among investment alternatives permitted from time to time under the plan.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	RELATED PARTY TRANSACTIONS: Certain of Quanta’s operating units have entered into related party lease arrangements for operational facilities, typically with prior owners of certain acquired businesses. These lease agreements generally have terms of up to approximately 5 years and include renewal options. Related party lease expense for the years ended December 31, 2017 , 2016 and 2015 was $12.3 million , $8.7 million and $10.6 million , respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES: Investments in Affiliates and Other Entities As described in Note 11, Quanta holds investments in certain joint ventures with third parties for the purpose of providing infrastructure services under certain customer contracts. Losses incurred by these joint ventures are generally shared ratably based on the percentage ownership of the joint venture members. However, each member of the joint venture typically is jointly and severally liable for all of the obligations of the joint venture under the contract with the customer, and therefore can be liable for full performance of the contract with the customer. In circumstances where Quanta’s participation in a joint venture qualifies as a general partnership, the joint venture partners are jointly and severally liable for all of the obligations of the joint venture, including obligations owed to the customer or any other person or entity. Quanta is not aware of circumstances that would lead to future claims against it for material amounts in connection with these joint and several liabilities. In the joint venture arrangements entered into by Quanta, typically each joint venture party indemnifies the other party for any liabilities incurred in excess of the liabilities such other party is obligated to bear under the respective joint venture agreement. It is possible, however, that Quanta could be required to pay or perform obligations in excess of its share if the other party to the joint venture failed or refused to pay or perform its share of the obligations. Quanta is not aware of circumstances that would lead to future claims against it for material amounts that would not be indemnified. During 2014, a limited partnership in which Quanta is a partner was selected for an engineering, procurement and construction (EPC) electric transmission project to construct approximately 500 kilometers of transmission line and two 500 kV substations. Quanta will provide turnkey EPC services for the entire project. As of December 31, 2017 , Quanta made aggregate contributions to this unconsolidated affiliate of $66.7 million , received $64.4 million as a return of capital and had outstanding additional capital commitments associated with this project of $25.2 million , which are anticipated to be paid in 2019. Additionally, as of December 31, 2017 , Quanta had outstanding capital commitments associated with investments in unconsolidated affiliates related to planned oil and gas infrastructure projects of $16.9 million , of which $14.8 million is expected to be paid in 2018 . The remaining $2.1 million of these capital commitments is anticipated to be paid by May 31, 2022 . As described in Note 2, Quanta formed a partnership with select infrastructure investors that provides up to $1.0 billion of capital, including approximately $80.0 million from Quanta, available to invest in certain specified infrastructure projects through August 2024. Leases Quanta leases certain land, buildings and equipment under non-cancelable lease agreements, including related party leases as discussed in Note 14. The terms of these agreements vary from lease to lease, including some with renewal options and escalation clauses. The following schedule shows the future minimum lease payments under these leases as of December 31, 2017 (in thousands): Operating Leases Year Ending December 31: 2018 $ 115,985 2019 75,556 2020 49,287 2021 28,422 2022 15,883 Thereafter 30,871 Total minimum lease payments $ 316,004 Rent expense related to operating leases was $276.2 million , $242.3 million and $208.5 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Quanta has guaranteed the residual value on certain of its equipment operating leases. Quanta has agreed to pay any difference between this residual value and the fair market value of the underlying asset at the date of termination of the leases. At December 31, 2017 , the maximum guaranteed residual value was $626.8 million . Quanta believes that no significant payments will be made as a result of the difference between the fair market value of the leased equipment and the guaranteed residual value. However, there can be no assurance that significant payments will not be required in the future. Contingent Consideration Liabilities As discussed in further detail in Note 2, Quanta is obligated to pay contingent consideration amounts to the former owners of certain acquired businesses in the event that such acquired businesses achieve specified financial performance metrics. As of December 31, 2017 and 2016 , the estimated fair value of Quanta’s contingent consideration liabilities totaled $65.7 million and $19.5 million . Committed Expenditures Quanta has capital commitments for the expansion of its vehicle fleet in order to accommodate manufacturer lead times on certain types of vehicles. As of December 31, 2017 , Quanta issued $14.6 million of production orders with expected delivery dates in 2018 . Although Quanta has committed to purchase these vehicles at the time of their delivery, Quanta anticipates that these orders will be assigned to third party leasing companies and made available to Quanta under certain of its master equipment lease agreements, thereby releasing Quanta from its capital commitments. Legal Proceedings Quanta is from time to time party to various lawsuits, claims and other legal proceedings that arise in the ordinary course of business. These actions typically seek, among other things, compensation for alleged personal injury, breach of contract and/or property damages, employment-related damages, punitive damages, civil penalties or other losses, or injunctive or declaratory relief. With respect to all such lawsuits, claims and proceedings, Quanta records a reserve when it is probable that a liability has been incurred and the amount of loss can be reasonably estimated. In addition, Quanta discloses matters for which management believes a material loss is at least reasonably possible. Except as otherwise stated below, none of these proceedings, separately or in the aggregate, are expected to have a material adverse effect on Quanta’s consolidated financial position, results of operations or cash flows. In all instances, management has assessed the matter based on current information and made a judgment concerning its potential outcome, giving due consideration to the nature of the claim, the amount and nature of damages sought and the probability of success. Management’s judgment may prove materially inaccurate, and such judgment is made subject to the known uncertainties of litigation. Maurepas Project Dispute . During the third quarter of 2017, Maurepas Pipeline, LLC (Maurepas) notified QPS Engineering, LLC (QPS), a subsidiary of Quanta, of Maurepas’ assertion of a claim for liquidated damages allegedly arising from delay in mechanical completion of a project in Louisiana. Quanta disputes the claim and believes that QPS is not responsible for liquidated damages under the contract terms. The matter remains subject to contractual dispute resolution measures; however, either party may choose to institute a formal legal proceeding upon completion of such measures. If, upon final resolution of this matter, Quanta is unsuccessful, any such liquidated damages would be recorded by QPS as additional costs on the project, and Quanta believes the range of reasonably possible loss could be up to $22.0 million , which is the maximum liability for liquidated damages pursuant to the contract terms. Lorenzo Benton v. Telecom Network Specialists, Inc., et al. In June 2006, plaintiff Lorenzo Benton filed a class action complaint in the Superior Court of California, County of Los Angeles, alleging various wage and hour violations against Telecom Network Specialists (TNS), a former subsidiary of Quanta. Quanta retained liability associated with this matter pursuant to the terms of Quanta’s sale of TNS in December 2012. Benton represents a class of workers that includes all persons who worked on certain TNS projects, including individuals that TNS retained through numerous staffing agencies. The plaintiff class in this matter is seeking damages for unpaid wages, penalties associated with the failure to provide meal and rest periods and overtime wages, interest and attorneys’ fees. In January 2017, the trial court granted a summary judgment motion filed by the plaintiff class and found that TNS was a joint employer of the class members and that it failed to provide adequate meal and rest breaks and failed to pay overtime wages. In February 2018, a hearing was held on a final motion for summary judgment on damages filed by the plaintiff class seeking approximately $11.1 million for its claims; however, a final determination regarding the amount of damages was not made. Quanta believes the court’s decision on liability is not supported by controlling law and continues to contest its liability and the damage calculation asserted by the plaintiff class in this matter. Additionally, in November 2007, TNS filed cross complaints for indemnity and breach of contract against the staffing agencies, which employed many of the individuals in question. In December 2012, the trial court heard cross-motions for summary judgment filed by TNS and the staffing agencies pertaining to TNS’s demand for indemnity. The court denied TNS’s motion and granted the motions filed by the staffing agencies; however, the California Appellate Court reversed the trial court’s decision in part and instructed the trial court to reconsider its ruling. In February 2017, the court denied a new motion for summary judgment filed by the staffing companies and has since stated that the staffing companies would be liable to TNS for any damages owed to the class members that the staffing companies employed. The final amount of liability, if any, payable in connection with this matter remains the subject of pending litigation and will ultimately depend on various factors, including the outcome of Quanta’s appeal of the trial court’s ruling on liability, the final determination with respect to any damages owed by Quanta, and the solvency of the staffing agencies. Based on review and analysis of the trial court’s rulings on liability, Quanta does not believe, at this time, that it is probable this matter will result in a material loss. However, if Quanta is unsuccessful in this litigation and the staffing agencies are unable to fund damages owed to class members, Quanta believes the range of reasonably possible loss to Quanta upon final resolution of this matter could be up to approximately $11.1 million , plus attorneys’ fees and expenses of the plaintiff class. For additional information regarding other legal proceedings, see Collective Bargaining Agreements in this Note 15. Concentrations of Credit Risk Quanta is subject to concentrations of credit risk related primarily to its cash and cash equivalents and its net receivable position with customers, which includes amounts related to billed and unbilled accounts receivable and costs and estimated earnings in excess of billings on uncompleted contracts net of advanced billings with the same customer. Substantially all of Quanta’s cash and cash equivalents are managed by what it believes to be high credit quality financial institutions. In accordance with Quanta’s investment policies, these institutions are authorized to invest cash and cash equivalents in a diversified portfolio of what Quanta believes to be high quality cash and cash equivalent investments, which consist primarily of interest-bearing demand deposits, money market investments, money market mutual funds and investment grade commercial paper with original maturities of three months or less. Although Quanta does not currently believe the principal amount of these cash and cash equivalents is subject to any material risk of loss, changes in economic conditions could impact the interest income Quanta receives from these investments. In addition, Quanta grants credit under normal payment terms, generally without collateral, to its customers, which include electric power and oil and gas companies, governmental entities, general contractors, and builders, owners and managers of commercial and industrial properties located primarily in the United States, Canada, Australia and Latin America. Consequently, Quanta is subject to potential credit risk related to changes in business and economic factors throughout these locations, which may be heightened as a result of uncertain economic and financial market conditions that have existed in recent years. However, Quanta generally has certain statutory lien rights with respect to services provided. Historically, some of Quanta’s customers have experienced significant financial difficulties, and others may experience financial difficulties in the future. These difficulties expose Quanta to increased risk related to collectability of billed and unbilled receivables and costs and estimated earnings in excess of billings on uncompleted contracts for services Quanta has performed. At December 31, 2016 , one customer within Quanta’s Electric Power Infrastructure Services segment accounted for 16% of Quanta’s consolidated net receivable position. Portions of this net receivable balance were related to invoicing challenges and billing delays on two electric transmission projects located in remote regions of northeastern Canada, which resulted from changed site conditions requiring extensive quality assurance documentation and administrative requirements. During the second quarter of 2017, Quanta and the customer reached a settlement and entered into a renegotiated contract, which eliminated the previous scheduling and billing issues and settled outstanding change orders. No other customers represented 10% or more of Quanta’s consolidated net receivable position as of December 31, 2017 or 2016 , and no customers represented 10% or more of Quanta’s consolidated revenues for the years ended December 31, 2017 , 2016 or 2015 . Insurance As discussed in Note 2, Quanta is insured for employer’s liability, workers’ compensation, auto liability, general liability and group health claims. As of December 31, 2017 and 2016 , the gross amount accrued for insurance claims totaled $254.7 million and $218.2 million , with $200.0 million and $162.0 million considered to be long term and included in “Insurance and other non-current liabilities.” Related insurance recoveries/receivables as of December 31, 2017 and 2016 were $50.4 million and $8.7 million , of which $0.4 million and $0.4 million were included in “Prepaid expenses and other current assets” and $50.0 million and $8.3 million were included in “Other assets, net.” Letters of Credit Certain of Quanta’s vendors require letters of credit to ensure reimbursement for amounts they are disbursing on Quanta’s behalf, such as to beneficiaries under its insurance programs. In addition, from time to time, certain customers require Quanta to post letters of credit to ensure payment of subcontractors and vendors and guarantee performance under contracts. Such letters of credit are generally issued by a bank or similar financial institution, typically pursuant to Quanta’s senior secured revolving credit facility. Each letter of credit commits the issuer to pay specified amounts to the holder of the letter of credit if the holder demonstrates that Quanta has failed to perform specified actions. If this were to occur, Quanta would be required to reimburse the issuer of the letter of credit. Depending on the circumstances of such a reimbursement, Quanta may also be required to record a charge to earnings for the reimbursement. Quanta does not believe that it is likely that any material claims will be made under a letter of credit in the foreseeable future. As of December 31, 2017 , Quanta had $413.3 million in outstanding letters of credit and bank guarantees under its senior secured revolving credit facility securing its casualty insurance program and various contractual commitments. These are irrevocable stand-by letters of credit with maturities generally expiring at various times throughout 2018 . Upon maturity, it is expected that the majority of the letters of credit related to the casualty insurance program will be renewed for subsequent one-year periods. Performance Bonds and Parent Guarantees In certain circumstances, Quanta is required to provide performance bonds in connection with its contractual commitments. Quanta has indemnified its sureties for any expenses paid out under these performance bonds. These performance bonds expire at various times ranging from mechanical completion of the related projects to a period extending beyond contract completion in certain circumstances, and as such a determination of maximum potential amounts outstanding requires the use of certain estimates and assumptions. Such amounts can also fluctuate from period to period based upon the mix and level of Quanta’s bonded operating activity. As of December 31, 2017 , the total amount of the outstanding performance bonds was estimated to be approximately $3.0 billion . Quanta’s estimated maximum exposure as it relates to the value of the performance bonds outstanding is lowered on each bonded project as the cost to complete is reduced, and each of its commitments under the performance bonds generally extinguishes concurrently with the expiration of its related contractual obligation. The estimated cost to complete these bonded projects was approximately $869 million as of December 31, 2017 . Additionally, from time to time, Quanta guarantees the obligations of its wholly owned subsidiaries, including obligations in connection with certain contracts with customers, lease obligations, joint venture arrangements and, in some states, contractors’ licenses. Quanta is not aware of any material obligations for performance or payment asserted against it under any of these guarantees. Employment Agreements Quanta has various employment agreements with certain executives and other employees, which provide for compensation and certain other benefits and for severance payments under certain circumstances. Certain employment agreements also contain clauses that become effective upon a change in control of Quanta, and Quanta may be obligated to pay certain amounts to such employees upon the occurrence of any of the defined change in control events. Collective Bargaining Agreements Some of Quanta’s operating units are parties to various collective bargaining agreements with unions that represent certain of their employees. The collective bargaining agreements expire at various times and have typically been renegotiated and renewed on terms similar to those in the expiring agreements. From time to time, Quanta is a party to grievance actions based on claims arising out of the collective bargaining agreements. The agreements require the operating units to pay specified wages, provide certain benefits to their union employees and contribute certain amounts to multiemployer pension plans and employee benefit trusts. Quanta’s multiemployer pension plan contribution rates generally are specified in the collective bargaining agreements (usually on an annual basis), and contributions are made to the plans on a “pay-as-you-go” basis based on its union employee payrolls. The location and number of union employees that Quanta employs at any given time and the plans in which they may participate vary depending on the projects Quanta has ongoing at any time and the need for union resources in connection with those projects. Therefore, Quanta is unable to accurately predict its union employee payroll and the amount of the resulting multiemployer pension plan contribution obligation for future periods. The PPA also added special funding and operational rules generally applicable to plan years beginning after 2007 for multiemployer plans that are classified as “endangered,” “seriously endangered” or “critical” status based on multiple factors (including, for example, the plan’s funded percentage, cash flow position and whether it is projected to experience a minimum funding deficiency). Plans in these classifications must adopt measures to improve their funded status through a funding improvement or rehabilitation plan, as applicable, which may require additional contributions from employers (which may take the form of a surcharge on benefit contributions) and/or modifications to retiree benefits. Certain plans to which Quanta contributes or may contribute in the future are in “endangered,” “seriously endangered” or “critical” status. The amount of additional funds, if any, that Quanta may be obligated to contribute to these plans in the future cannot be estimated due to uncertainty of the future levels of work that require the specific use of union employees covered by these plans, as well as the future contribution levels and possible surcharges on contributions applicable to these plans. Quanta may be subject to additional liabilities imposed by law as a result of its participation in multiemployer defined benefit pension plans. For example, the Employee Retirement Income Security Act of 1974, as amended by the Multiemployer Pension Plan Amendments Act of 1980, imposes certain liabilities upon an employer who is a contributor to a multiemployer pension plan if the employer withdraws from the plan or the plan is terminated or experiences a mass withdrawal. These liabilities include an allocable share of the unfunded vested benefits in the plan for all plan participants, not merely the benefits payable to a contributing employer’s own retirees. As a result, participating employers may bear a higher proportion of liability for unfunded vested benefits if other participating employers cease to contribute or withdraw, with the reallocation of liability being more acute in cases when a withdrawn employer is insolvent or otherwise fails to pay its withdrawal liability. Other than as described below, Quanta is not aware of any material amounts of withdrawal liability that have been incurred as a result of a withdrawal by any of Quanta’s operating units from any multiemployer defined benefit pension plans. 2011 Central States Plan Withdrawal Liability . In the fourth quarter of 2011, certain Quanta subsidiaries withdrew from the Central States Plan. This withdrawal event was the result of an amendment to a collective bargaining agreement with the International Brotherhood of Teamsters (Teamsters) that eliminated certain employers’ obligations to contribute to the Central States Plan, which was then in critical status and significantly underfunded as to its vested benefit obligations. The amendment was negotiated by the Pipe Line Contractors Association (PLCA) on behalf of its members, which include certain Quanta subsidiaries. Because certain other Quanta subsidiaries continued participation in the Central States Plan into 2012, the Quanta subsidiaries’ withdrawals in 2011 effected only a partial withdrawal on behalf of Quanta for 2011. Quanta believed that the partial withdrawal was advantageous because it limited exposure to increased liability resulting from a future withdrawal event, at which point the Central States Plan could have been further underfunded. Quanta and other PLCA members now contribute to a different multiemployer pension plan on behalf of the affected Teamsters employees. The Central States Plan subsequently asserted that the withdrawal of the PLCA members, and thus Quanta’s partial withdrawal, was not effective in 2011. The PLCA and Quanta believed at that time that a legally effective withdrawal had occurred during the fourth quarter of 2011, and this issue was litigated in the federal district court for the Northern District of Illinois, Eastern Division. In September 2013, the district court ruled in favor of the Central States Plan, and that decision was appealed by the PLCA. In July 2014, the Central States Plan provided Quanta with a Notice and Demand claiming partial withdrawal liability in the amount of $39.6 million and requiring Quanta to make payments on this assessment while the dispute was ongoing. In September 2015, the United States Court of Appeals for the Seventh Circuit ruled in favor of the PLCA and reversed the district court’s previous ruling. Based on the outcome of the appeal, in January 2016, the Central States Plan issued a revised Notice and Demand claiming a partial withdrawal liability in the amount of $32.9 million . Separately, in December 2013, the Central States Plan filed lawsuits against two of Quanta’s other subsidiaries in connection with their withdrawal in 2012. In the first lawsuit, the Central States Plan alleged that the subsidiary elected to participate in the Central States Plan pursuant to the collective bargaining agreement under which it participated. Quanta argued that no such election was made and that any payments made to the Central States Plan were made in error. In July 2014, the parties reached an agreement to settle the lawsuit, and the court dismissed the case with prejudice. In the second lawsuit, the Central States Plan alleged that contributions made by the Quanta subsidiary to a new industry fund created after Quanta withdrew from the Central States Plan should have been made to the Central States Plan. This arguably would have extended the withdrawal date for this subsidiary to at least the end of 2013. Quanta disputed these allegations on the basis that it properly paid contributions to the new industry fund based on the terms of the collective bargaining agreement under which it participated and asserted that it terminated its obligation to contribute to the Central States Plan by the end of 2012. The parties both moved for summary judgment, and in March 2015, the court entered judgment in favor of Quanta. The Central States Plan filed a notice of appeal in April 2015, and in December 2015, the Central States Plan agreed to dismiss the appeal with prejudice. In December 2017, Quanta and the Central States Plan entered into a settlement agreement and release, whereby the parties agreed on a final settlement amount of $48.9 million , which included a final withdrawal liability of $44.1 million and retention of interest paid on the assessed amount of $4.8 million . This settlement addressed (i) the partial withdrawal liability assessed in the January 2016 Notice and Demand; (ii) an unassessed withdrawal liability in connection with a partial withdrawal in 2012; and (iii) an unassessed withdrawal liability in connection with a complete withdrawal in 2013 or 2014. Prior to settlement of the matter, Quanta made monthly payments on the assessed partial withdrawal liability according to the terms of the January 2016 Notice and Demand, and the portion of those payments that was attributable to the principal amount of the assessed liability was offset against its final withdrawal liability. Accordingly, a final payment of $25.5 million was made in December 2017 as full satisfaction of this matter. 2013 Central States Plan Withdrawal Liability. On October 9, 2013, Quanta acquired a company that experienced a complete withdrawal from the Central States Plan prior to the acquisition date. Prior to the acquisition, the Central States Plan issued a Notice and Demand to the acquired company claiming a withdrawal liability in the total amount of $6.9 million and requiring payments to be made on this assessment while the dispute is ongoing. In connection with the acquisition, Quanta recorded an initial liability of $4.8 million related to this withdrawal liability, and a portion of the purchase price for the acquired company was deposited into an escrow account to fund any withdrawal obligation in excess of the initial liability recorded. In January 2016, the Central States Plan issued a revised Notice and Demand claiming a withdrawal liability in the amount of $4.8 million . Although Quanta continues to dispute the total liability owed to the Central States Plan, it continues to make monthly payments according to the terms of this revised Notice and Demand while the parties determine the final withdrawal liability. As of December 31, 2017 , payments totaling $4.2 million had been made toward the withdrawal liability assessment. The final amount of withdrawal liability payable in connection with this matter remains the subject of a pending arbitration proceeding and will ultimately depend on various factors, including the outcome of the arbitration. However, the acquired company’s withdrawal from the Central States Plan is not expected to have a material impact on Quanta’s financial condition, results of operations or cash flows. Indemnities Quanta generally indemnifies its customers for the services it provides under its contracts, as well as other specified liabilities, which may subject Quanta to indemnity claims and liabilities and related litigation. Additionally, in connection with certain acquisitions and dispositions, Quanta has indemnified various parties against specified liabilities that those parties might incur in the future. The indemnities under acquisition or disposition agreements are usually contingent upon the other party incurring liabilities that reach specified thresholds. As of December 31, 2017 , except as otherwise set forth above in Legal Proceedings , Quanta does not believe any material liabilities for claims exist against it in connection with any of these indemnity obligations. In the normal course of Quanta’s acquisition transactions, Quanta obtains rights to indemnification from the sellers or former owners of acquired companies for certain risks, liabilities and obligations arising from their prior operations, such as performance, operational, safety, workforce or tax issues, some of which Quanta may not have discovered during due diligence. However, the indemnities may not cover all of Quanta’s exposure for such pre-acquisition matters, and the indemnitors may be unwilling or unable to pay the amounts owed to Quanta. Accordingly, Quanta may incur expenses for which it is not reimbursed. Quanta is currently in the process of negotiating certain pre-acquisition obligations associated with non-U.S. payroll taxes that may be due from a business acquired by Quanta in 2013. As of December 31, 2017 , Quanta had recorded $11.4 million as its estimate of the pre-acquisition tax obligations and a corresponding indemnification asset, as management expects to recover from the indemnity counterparties any amounts that Quanta may be required to pay in connection with any such obligations.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Information	SEGMENT INFORMATION: Quanta presents its operations under two reportable segments: (1) Electric Power Infrastructure Services and (2) Oil and Gas Infrastructure Services. This structure is generally based on the broad end-user markets for Quanta’s services. See Note 1 for additional information regarding Quanta’s reportable segments. Quanta’s segment results are derived from the types of services provided across its operating units in each of the end user markets described above. Quanta’s entrepreneurial business model allows each of its operating units to serve the same or similar customers and to provide a range of services across end user markets. Quanta’s operating units are organized into one of two internal divisions, namely, the Electric Power Infrastructure Services Division and the Oil and Gas Infrastructure Services Division. These internal divisions are closely aligned with the reportable segments and are based on their operating units’ predominant type of work. Reportable segment information, including revenues and operating income by type of work, is gathered from each operating unit for the purpose of evaluating segment performance in support of Quanta’s market strategies. These classifications of Quanta’s operating unit revenues by type of work for segment reporting purposes can at times require judgment on the part of management. Quanta’s operating units may perform joint projects for customers in multiple industries, deliver multiple types of services under a single customer contract or provide service across industries. For example, Quanta performs joint trenching projects to install distribution lines for electric power and natural gas customers. In addition, Quanta’s integrated operations and common administrative support at each of its operating units require that certain allocations be made to determine segment profitability, including allocations of shared and indirect costs, such as facility costs, indirect operating expenses including depreciation, and general and administrative costs. Corporate costs, such as payroll and benefits, employee travel expenses, facility costs, professional fees, acquisition costs and amortization related to intangible assets are not allocated. Summarized financial information for Quanta’s reportable segments is presented in the following table (in thousands): Year Ended December 31, 2017 2016 2015 Revenues: Electric Power Infrastructure Services $ 5,599,836 $ 4,850,495 $ 4,937,289 Oil and Gas Infrastructure Services 3,866,642 2,800,824 2,635,147 Consolidated $ 9,466,478 $ 7,651,319 $ 7,572,436 Operating income (loss) : Electric Power Infrastructure Services $ 518,130 $ 395,745 $ 362,328 Oil and Gas Infrastructure Services 184,083 149,502 142,929 Corporate and non-allocated costs (323,364 ) (224,434 ) (267,754 ) Consolidated $ 378,849 $ 320,813 $ 237,503 Depreciation: Electric Power Infrastructure Services $ 91,708 $ 91,269 $ 89,150 Oil and Gas Infrastructure Services 76,355 67,374 65,315 Corporate and non-allocated costs 15,745 11,597 8,380 Consolidated $ 183,808 $ 170,240 $ 162,845 Separate measures of Quanta’s assets and cash flows by reportable segment, including capital expenditures, are not produced or utilized by management to evaluate segment performance. Quanta’s fixed assets, which are held at the operating unit level, include operating machinery, equipment and vehicles, as well as office equipment, buildings and leasehold improvements, and are used on an interchangeable basis across its reportable segments. As such, for reporting purposes, total depreciation expense is allocated each quarter among Quanta’s reportable segments based on the ratio of each reportable segment’s revenue contribution to consolidated revenues. Foreign Operations During 2017 , 2016 , and 2015 , Quanta derived $2.48 billion , $1.59 billion and $1.54 billion , respectively, of its revenues from foreign operations. Of Quanta’s foreign revenues, 79% , 75% and 85% were earned in Canada during the years ended December 31, 2017 , 2016 and 2015 , respectively. In addition, Quanta held property and equipment of $330.4 million and $320.7 million in foreign countries, primarily Canada, as of December 31, 2017 and 2016 .

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	SUPPLEMENTAL CASH FLOW INFORMATION: The net effect of changes in operating assets and liabilities, net of non-cash transactions, on cash flows from operating activities of continuing operations is as follows (in thousands): Year Ended December 31, 2017 2016 2015 Accounts and notes receivable $ (425,313 ) $ 144,877 $ 150,470 Costs and estimated earnings in excess of billings on uncompleted contracts 15,999 (152,702 ) (49,358 ) Inventories 14,110 (9,905 ) (33,524 ) Prepaid expenses and other current assets (32,079 ) 25,133 5,899 Accounts payable and accrued expenses and other non-current liabilities 29,722 81,792 7,311 Billings in excess of costs and estimated earnings on uncompleted contracts 139,114 (124,680 ) 153,017 Other, net 17,267 (13,743 ) (11,707 ) Net change in operating assets and liabilities, net of non-cash transactions $ (241,180 ) $ (49,228 ) $ 222,108 Additional supplemental cash flow information is as follows (in thousands): Year Ended December 31, 2017 2016 2015 Cash (paid) received during the period for - Interest paid related to continuing operations $ (19,373 ) $ (12,828 ) $ (7,087 ) Income taxes paid related to continuing operations $ (112,335 ) $ (121,662 ) $ (130,921 ) Income taxes paid related to discontinued operations $ — $ (7,260 ) $ (144,076 ) Income tax refunds related to continuing operations $ 9,845 $ 7,548 $ 23,788 During the year ended December 31, 2017 , Quanta entered into a non-cash transaction whereby Quanta accepted title to a marine vessel in satisfaction and discharge of a $7.1 million note receivable.

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (Unaudited)	QUARTERLY FINANCIAL DATA (UNAUDITED): The table below sets forth the unaudited consolidated operating results by quarter for the years ended December 31, 2017 and 2016 (in thousands, except per share information). For the Three Months Ended March 31, June 30, September 30, December 31, 2017: Revenues $ 2,178,170 $ 2,200,374 $ 2,609,307 $ 2,478,627 Gross profit 266,188 302,165 350,631 322,876 Net income 48,440 64,360 89,849 115,576 Net income attributable to common stock 48,267 63,837 89,313 113,561 Net income from continuing operations attributable to common stock 48,267 63,837 89,313 113,561 Basic earnings per share from continuing operations attributable to common stock $ 0.31 $ 0.41 $ 0.57 $ 0.72 Diluted earnings per share from continuing operations attributable to common stock $ 0.31 $ 0.41 $ 0.56 $ 0.72 2016: Revenues $ 1,713,737 $ 1,792,430 $ 2,042,186 $ 2,102,966 Gross profit 203,313 200,217 302,582 307,688 Net income 20,859 16,729 74,152 88,358 Net income attributable to common stock 20,496 16,562 73,742 87,583 Net income from continuing operations attributable to common stock 20,496 16,562 73,137 88,530 Basic earnings per share from continuing operations attributable to common stock $ 0.13 $ 0.11 $ 0.47 $ 0.57 Diluted earnings per share from continuing operations attributable to common stock $ 0.13 $ 0.11 $ 0.47 $ 0.57 During the fourth quarter of 2017, Quanta recorded one-time tax benefits as further described in Note 10 and asset impairment charges of $58.1 million ( $36.6 million net of tax), which were primarily associated with two reporting units within its Oil and Gas Infrastructure Services Division. Specifically, a reporting unit that provides material handling services experienced lower operating margins and is expected to continue to face a highly competitive environment in its select markets, and a reporting unit that provides marine and offshore services experienced prolonged periods of reduced revenues and operating margins and is expected to continue to experience lower levels of activity in the U.S. Gulf of Mexico and other offshore markets. During the fourth quarter of 2016, Quanta recorded total asset impairment charges of $8.0 million ( $7.1 million net of tax) primarily related to a pending disposition of certain international renewable energy services operations, which was completed in 2017. The sum of the individual quarterly earnings per share amounts may not equal year-to-date earnings per share as each period’s computation is based on the weighted average number of shares outstanding during the period.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS: Acquisitions In January 2018, Quanta acquired an electrical infrastructure services business specializing in substation construction and relay services and a postsecondary educational institution that provides pre-apprenticeship training and programs for experienced lineman, both of which are located in the United States. The aggregate consideration for these acquisitions was $47.9 million in cash, subject to certain adjustments, and 379,817 shares of Quanta common stock, which had a fair value of approximately $13.6 million at the acquisition dates. Additionally, the acquisition of the postsecondary educational institution includes the potential payment of up to approximately $15.0 million , payable if the acquired business achieves certain financial and operational objectives over a five-year period. The results of the acquired businesses will generally be included in Quanta’s Electric Power Infrastructure Services segment and consolidated financial statements beginning on the acquisition dates. Due to the recent closing of these acquisitions, certain financial information related to these acquisitions, including the fair value of total consideration transferred or estimated to be transferred, is not yet finalized.

Summary of Significant Accoun28

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The consolidated financial statements of Quanta include the accounts of Quanta Services, Inc. and its wholly owned subsidiaries, which are also referred to as its operating units. The consolidated financial statements also include the accounts of certain of Quanta’s investments in joint ventures, which are either consolidated or proportionately consolidated, as discussed in the following summary of significant accounting policies. Investments in affiliated entities in which Quanta does not have a controlling financial interest, but over which Quanta has significant influence, usually because Quanta holds a voting interest of between 20% and 50%, are accounted for using the equity method. All significant intercompany accounts and transactions have been eliminated in consolidation. Unless the context requires otherwise, references to Quanta include Quanta Services, Inc. and its consolidated subsidiaries.
Reclassifications	Reclassifications Quanta reclassified certain prior period amounts related to stock-based compensation in the accompanying consolidated statements of cash flows to conform to the current period presentation under a recently adopted accounting update. Additionally, certain reclassifications have been made to Quanta’s prior year’s consolidated statements of operations to conform to classifications in the current year.
Use of Estimates and Assumptions	Use of Estimates and Assumptions The preparation of financial statements in conformity with US GAAP requires the use of estimates and assumptions by management in determining the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities known to exist as of the date the financial statements are published, and the reported amounts of revenues and expenses recognized during the periods presented. Quanta reviews all significant estimates affecting its consolidated financial statements on a recurring basis and records the effect of any necessary adjustments prior to their publication. Judgments and estimates are based on Quanta’s beliefs and assumptions derived from information available at the time such judgments and estimates are made. Uncertainties with respect to such estimates and assumptions are inherent in the preparation of financial statements. Estimates are primarily used in Quanta’s assessment of the allowance for doubtful accounts, valuation of inventory, useful lives of assets, fair value assumptions in analyzing goodwill, other intangibles and long-lived asset impairments, equity and other investments, loan receivables, purchase price allocations, acquisition-related contingent consideration liabilities, liabilities for insurance and other claims and guarantees, multiemployer pension plan withdrawal liabilities, revenue recognition for construction contracts inclusive of contractual change orders and claims, share-based compensation, operating results of reportable segments, as well as the provision for income taxes and the calculation of uncertain tax positions.
Cash and Cash Equivalents	Cash and Cash Equivalents Quanta had cash and cash equivalents of $138.3 million and $112.2 million as of December 31, 2017 and 2016 . Cash consisting of interest-bearing demand deposits is carried at cost, which approximates fair value. Quanta considers all highly liquid investments with an original maturity of three months or less at the time of purchase to be cash equivalents, which are carried at fair value. At December 31, 2017 and 2016 , cash equivalents were $7.1 million and $8.8 million and consisted primarily of money market investments and money market mutual funds and are discussed further in Fair Value Measurements below. As of December 31, 2017 and 2016 , cash and cash equivalents held in domestic bank accounts were $83.1 million and $19.5 million , and cash and cash equivalents held in foreign bank accounts were $55.2 million and $92.7 million . As of December 31, 2017 and 2016 , cash and cash equivalents held by joint ventures, which are either consolidated or proportionately consolidated, were $16.7 million and $11.5 million , of which $10.0 million and $10.0 million related to domestic joint ventures. Cash and cash equivalents held by the joint ventures are available to support joint venture operations, but Quanta cannot utilize those assets to support its other operations. Quanta generally has no right to the joint ventures’ cash and cash equivalents other than participating in distributions and in the event of dissolution.
Current and Long-Term Accounts and Notes Receivable and Allowance for Doubtful Accounts	Current and Long-Term Accounts and Notes Receivable and Allowance for Doubtful Accounts Quanta provides an allowance for doubtful accounts when collection of an account or note receivable is considered doubtful, and receivables are written off against the allowance when deemed uncollectible. Inherent in the assessment of the allowance for doubtful accounts are certain judgments and estimates regarding, among other factors, the customer’s access to capital, the customer’s willingness or ability to pay, general economic and market conditions, the ongoing relationship with the customer and uncertainties related to the resolution of disputed matters. Quanta considers accounts receivable delinquent after 30 days but does not generally include delinquent accounts in its analysis of the allowance for doubtful accounts unless the accounts receivable have been outstanding for at least 90 days. Quanta also includes accounts receivable balances that relate to customers in bankruptcy or with other known difficulties in its analysis of the allowance for doubtful accounts. Material changes in customers’ business or cash flows, which may be impacted by negative economic and market conditions, could affect Quanta’s ability to collect amounts due. As of December 31, 2017 and 2016 , Quanta had allowances for doubtful accounts on current receivables of $4.5 million and $2.8 million . Long-term accounts receivable are included within “Other assets, net” in the accompanying consolidated balance sheets. Should customers experience financial difficulties or file for bankruptcy, or should anticipated recoveries relating to receivables in existing bankruptcies or other workout situations fail to materialize, Quanta could experience reduced cash flows and losses in excess of current allowances provided. The balances billed but not paid by customers pursuant to retainage provisions in certain contracts are generally due upon completion of the contracts and acceptance by the customer. Based on Quanta’s experience with similar contracts in recent years, the majority of the retainage balances at each balance sheet date are expected to be collected within the next twelve months. Current retainage balances as of December 31, 2017 and 2016 were $300.5 million and $231.0 million and were included in “Accounts receivable.” Retainage balances with settlement dates beyond the next twelve months were included in “Other assets, net,” and as of December 31, 2017 and 2016 were $41.9 million and $5.2 million . Within accounts receivable, Quanta recognizes unbilled receivables in circumstances such as when revenues have been earned and recorded but the amount cannot be billed under the terms of the contract until a later date; costs have been incurred but are yet to be billed under cost-reimbursement type contracts; or amounts arise from routine lags in billing (for example, work completed one month but not billed until the next month). These balances do not include revenues accrued for work performed under fixed-price contracts as these amounts are recorded as “Costs and estimated earnings in excess of billings on uncompleted contracts.” At December 31, 2017 and 2016 , the balances of unbilled receivables included in “Accounts receivable” were $303.9 million and $206.8 million .
Inventories	Inventories Inventories consist primarily of parts and supplies held for use in the ordinary course of business, which are valued by Quanta at the lower of cost or net realizable value. Cost is determined by using either the first-in, first-out (FIFO) method or the average costing method. Inventories also include certain job specific materials not yet installed which are valued using the specific identification method.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, and depreciation is computed using the straight-line method, net of estimated salvage values, over the estimated useful lives of the assets. Leasehold improvements are capitalized and amortized over the lesser of the life of the lease or the estimated useful life of the asset. Depreciation expense related to property and equipment was $183.8 million , $170.2 million and $162.8 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Accrued capital expenditures were $9.6 million and $12.7 million as of December 31, 2017 and 2016 . The impact of these items has been excluded from Quanta’s capital expenditures in the accompanying consolidated statements of cash flows due to their non-cash nature. Expenditures for repairs and maintenance are charged to expense when incurred. Expenditures for major renewals and betterments, which extend the useful lives of existing equipment, are capitalized and depreciated over the adjusted remaining useful lives of the assets. Upon retirement or disposition of property and equipment, the cost and related accumulated depreciation are removed from the accounts and any resulting gain or loss is reflected in selling, general and administrative expenses. Management reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount may not be realizable. Quanta also recorded asset impairments primarily related to certain international renewable energy services operations of $8.0 million in 2016 and $6.6 million in 2015. The 2016 impairment was primarily due to a pending disposition of certain international renewable energy services operations that was completed in 2017, and the 2015 impairment was based on the estimated future undiscounted cash flows for the asset group as compared to their carrying amount. When an evaluation is required, the estimated future undiscounted cash flows associated with the asset group are compared to the asset group’s carrying amount to determine if an impairment of such asset group is necessary. The effect of any impairment involves expensing the difference between the fair value of such asset group and its carrying amount in the period incurred.
Other Assets, Net	Other Assets, Net Other assets, net consists primarily of long-term receivables, long-term retainage, deferred tax assets, debt issuance costs, equity and other investments, refundable security deposits for leased properties and insurance claims in excess of deductibles that are due from Quanta’s insurers.
Debt Issuance Costs	Debt Issuance Costs Capitalized debt issuance costs related to Quanta’s senior secured revolving credit facility and any other debt outstanding at a given balance sheet date are included in other assets, net and are amortized into interest expense on a straight-line basis over the terms of the respective agreements giving rise to the debt issuance costs, which Quanta believes approximates the effective interest rate method.
Goodwill and Other Intangible Assets	Goodwill Quanta has recorded goodwill in connection with its historical acquisitions of companies. Upon acquisition, these companies were either combined into one of Quanta’s existing operating units or managed on a stand-alone basis as an individual operating unit. Goodwill recorded in connection with these acquisitions is subject to an annual assessment for impairment, which Quanta performs at the operating unit level for each operating unit that carries a balance of goodwill. Each of Quanta’s operating units is organized into one of two internal divisions: the Electric Power Infrastructure Services Division and the Oil and Gas Infrastructure Services Division. As most of the companies acquired by Quanta provide multiple types of services for multiple types of customers, these divisional designations are based on the predominant type of work performed by each operating unit at the point in time the divisional designation is made. Goodwill is required to be measured for impairment at the reporting unit level, which represents the operating segment level or one level below the operating segment level for which discrete financial information is available. Quanta has determined that its individual operating units represent its reporting units for the purpose of assessing goodwill impairments. In January 2017, the Financial Accounting Standards Board (FASB) issued an update intended to simplify the subsequent measurement of goodwill by eliminating the second step in the two-step goodwill impairment test. The update requires an entity to perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and to recognize an impairment charge for the amount by which the carrying amount exceeds the fair value. The income tax effect associated with an impairment of tax deductible goodwill is also considered in the measurement of the goodwill impairment. Quanta elected to adopt the provisions of the update in connection with its annual impairment test performed in the fourth quarter of 2017. Quanta has the option to first assess qualitative factors to determine whether it is necessary to perform the quantitative fair value-based impairment test described below. If Quanta believes that, as a result of its qualitative assessment, it is more likely than not that the fair value of a reporting unit is less than its carrying amount, the quantitative impairment test is required. Quanta can choose to perform the qualitative assessment on none, some, or all of its reporting units. Quanta can also bypass the qualitative assessment for any reporting unit in any period and proceed directly to the quantitative impairment test, and then resume the qualitative assessment in any subsequent period. Qualitative indicators including deterioration in macroeconomic conditions, declining financial performance, or a sustained decrease in share price, among other things, may trigger the need for annual or interim impairment testing of goodwill associated with one or all of the reporting units. Quanta’s annual goodwill impairment assessment is performed in the fourth quarter of its fiscal year, or more frequently if events or circumstances arise which indicate that goodwill may be impaired. For instance, a decrease in Quanta’s market capitalization below book value, a significant change in business climate or loss of a significant customer, as well as the qualitative indicators referenced above, may trigger the need for interim impairment testing of goodwill for a reporting unit. The quantitative impairment test involves comparing the fair value of each of Quanta’s reporting units with its carrying amount, including goodwill. If the carrying amount of a reporting unit exceeds its fair value, an impairment loss is recorded as a reduction to goodwill with a corresponding charge to “Asset impairment charges” in the accompanying consolidated statements of operations. Any goodwill impairment is limited to the total amount of goodwill allocated to that reporting unit. Quanta determines the fair value of its reporting units using a weighted combination of the discounted cash flow, market multiple and market capitalization valuation approaches, with heavier weighting on the discounted cash flow method because management believes this method results in the most accurate calculation of fair value. Determining the fair value of a reporting unit requires judgment and the use of significant estimates and assumptions, including revenue growth rates, operating margins, discount rates, weighted average costs of capital and future market conditions. Quanta believes the estimates and assumptions used in its impairment assessments are reasonable and based on available market information, but variations in any of the assumptions could result in materially different calculations of fair value and determinations of whether or not an impairment is indicated. Under the discounted cash flow method, Quanta determines fair value based on the estimated future cash flows of each reporting unit, discounted to present value using risk-adjusted industry discount rates, which reflect the overall level of inherent risk of a reporting unit and the rate of return an outside investor would expect to earn. Cash flow projections are derived from budgeted amounts and operating forecasts (typically a one-year model) plus an estimate of later period cash flows, all of which are evaluated by management. Subsequent period cash flows are developed for each reporting unit using growth rates that management believes are reasonably likely to occur, along with a terminal value derived from the reporting unit’s earnings before interest, taxes, depreciation and amortization (EBITDA). The EBITDA multiples for each reporting unit are based on trailing twelve-month comparable industry data. Under the market multiple and market capitalization approaches, Quanta determines the estimated fair value of each of its reporting units by applying transaction multiples to each reporting unit’s projected EBITDA and then averaging that estimate with similar historical calculations using either a one, two or three year average. For the market capitalization approach, Quanta adds a reasonable control premium, which is estimated as the premium that would be received in a sale of the reporting unit in an orderly transaction between market participants. The projected cash flows and estimated levels of EBITDA by reporting unit were used to determine fair value under the three approaches discussed herein. The following table presents the significant estimates used by management in determining the fair values of Quanta’s reporting units at December 31, 2017 , 2016 and 2015 : 2017 2016 2015 Years of cash flows before terminal value 5 years 5 years 5 years Discount rates 12.0% to 14.0% 12.5% to 14.5% 12.0% to 16.0% EBITDA multiples 5.5 to 7.0 5.5 to 7.0 5.0 to 6.5 Weighting of three approaches: Discounted cash flows 70% 70% 70% Market multiple 15% 15% 15% Market capitalization 15% 15% 15% For recently acquired reporting units, a quantitative impairment test may indicate a fair value that is substantially similar to the reporting unit’s carrying amount. Such similarities in value are generally an indication that management’s estimates of future cash flows associated with the recently acquired reporting unit remain relatively consistent with the assumptions that were used to derive its initial fair value. During the fourth quarter of 2017 , a quantitative fair-value based goodwill impairment analysis was performed for each of Quanta’s reporting units, and no reporting units were evaluated solely on a qualitative basis. The analysis indicated that the fair value of each of Quanta’s reporting units, with the exception of two reporting units in its Oil and Gas Infrastructure Services Division, was in excess of its carrying amount. Quanta recorded a $57.0 million non-cash charge in the fourth quarter of 2017 for the impairment of goodwill associated with the two reporting units. Specifically, a reporting unit that provides material handling services experienced lower operating margins and is expected to continue to face a highly competitive environment in its select markets and a reporting unit that provides marine and offshore services experienced prolonged periods of reduced revenues and operating margins and is expected to continue to experience lower levels of activity in the U.S. Gulf of Mexico and other offshore markets. As discussed generally above, when evaluating the 2017 quantitative impairment test results, management considered many factors in determining whether an impairment of goodwill for any reporting unit was reasonably likely to occur in future periods, including future market conditions and the economic environment. Additionally, management considered the sensitivity of its fair value estimates to changes in certain valuation assumptions. After taking into account a 10% decrease in the fair value of each of Quanta’s reporting units, one additional reporting unit within Quanta’s Oil and Gas Infrastructure Services Division would have a fair value below its carrying amount. The fair value determined in 2017 for this reporting unit was consistent with the fair value determined in 2016 . Circumstances such as market declines, unfavorable economic conditions, loss of a major customer or other factors could increase the risk of impairment of goodwill for this reporting unit in future periods. If an operating unit experiences prolonged periods of declining revenues, operating margins or both, it may be at risk of failing the quantitative goodwill impairment test. In addition to the reporting units referenced above, certain operating units have experienced declines over the short-term due to challenging macroeconomic conditions in certain geographic areas and low oil and natural gas prices, which have negatively impacted customer spending and resulted in project cancellations and delays. Additionally, customer capital spending has been constrained as a result of an increasingly complex regulatory and permitting environment. Certain operating units within Quanta’s Oil and Gas Infrastructure Services Division that primarily operate within the midstream and smaller-scale transmission market, including the reporting unit referenced above, have continued to be negatively impacted by these factors. Goodwill and intangible assets associated with these operating units were $50.1 million and $14.7 million at December 31, 2017 . Quanta monitors these conditions and others to determine if it is necessary to perform the quantitative fair-value based impairment test for one or more operating units prior to the annual impairment assessment. Although Quanta is not aware of circumstances that would lead to additional goodwill impairments at this time, circumstances such as a continued market decline, the loss of a major customer or other factors could impact the valuation of goodwill in the future. The goodwill analysis performed for each reporting unit was based on estimates and comparisons obtained from the electric power and oil and gas industries. Quanta assigned a higher weighting to the discounted cash flow approach in all periods to reflect increased expectations of market value being determined from a “held and used” model. As stated previously, cash flows are derived from budgeted amounts and operating forecasts that have been evaluated by management. In connection with the 2017 assessment, reporting unit annual compounded revenue growth rates during the cash flow projection period varied from negative 14% to positive 17% . Estimating future cash flows requires significant judgment, and Quanta’s projections may vary from cash flows eventually realized. Changes in Quanta’s judgments and projections could result in a significantly different estimate of the fair values of reporting units and intangible assets and could result in an impairment. Variances in the assessment of market conditions, projected cash flows, cost of capital, growth rates and acquisition multiples applied could have an impact on the assessment of impairments and the amount of any goodwill impairment charges recorded. For example, lower growth rates, lower acquisition multiples or higher costs of capital assumptions would all individually lead to lower fair value assessments and potentially increased frequency or size of goodwill impairments. Goodwill impairments are included within “Asset impairment charges” on Quanta’s consolidated statements of operations. Based on the goodwill impairment analysis, Quanta compared the sum of fair values of its reporting units to its market capitalization at December 31, 2017 and determined that the excess of the aggregate fair value of all reporting units to its market capitalization reflected a reasonable control premium. Quanta’s market capitalization at December 31, 2017 was approximately $6.02 billion , and its total stockholders’ equity was approximately $3.79 billion . If the price of Quanta’s common stock were to decline to a level that causes its market capitalization to be lower than the value of its stockholders’ equity, this would be another factor that could increase the risk of further impairment of goodwill in future periods. Increases in the carrying amount of individual reporting units that may be indicated by Quanta’s impairment tests are not recorded, therefore Quanta may record goodwill impairments in the future, even when the aggregate fair value of its reporting units as a whole may increase. During the fourth quarter of 2015, management concluded that goodwill was impaired at two reporting units in Quanta’s Oil and Gas Infrastructure Services Division and recorded a $39.8 million non-cash charge for the impairment of goodwill, which primarily resulted from lower levels of expected activity in the U.S. Gulf of Mexico and, to a lesser extent, the extended low commodity price environment for certain directional drilling operations in Australia. Other Intangible Assets Quanta’s intangible assets include customer relationships, backlog, trade names, non-compete agreements, patented rights and developed technology, all of which are subject to amortization. The value of customer relationships is estimated as of the date a business is acquired based on the value-in-use concept utilizing the income approach, specifically the excess earnings method. This analysis discounts to present value the projected cash flows attributable to the customer relationships, with consideration given to customer contract renewals and estimated customer attrition rates. The following table presents the significant estimates used by management in determining the fair values of customer relationships associated with acquisitions in the years ended December 31, 2017 , 2016 and 2015 : 2017 2016 2015 Discount rates 17% to 25% 20% to 23% 18% to 22% Customer attrition rates 15% to 78% 10% to 70% 14% to 70% Quanta values backlog for acquired businesses as of the acquisition date based upon the contractual nature of the backlog within each service line, discounted to present value. The value of trade names is estimated using the relief-from-royalty method of the income approach. This approach is based on the assumption that in lieu of ownership, a company would be willing to pay a royalty for use of the trade name. Quanta amortizes intangible assets based upon the estimated consumption of their economic benefits, or on a straight-line basis if the pattern of economic benefit cannot otherwise be reliably estimated. Intangible assets subject to amortization are reviewed for impairment and tested for recoverability whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. For instance, a significant change in business climate or a loss of a significant customer, among other things, may trigger the need for interim impairment testing of intangible assets. An impairment loss is recognized if the carrying amount of an intangible asset is not recoverable and its carrying amount exceeds its fair value. Intangible asset impairments are included within “Asset impairment charges” in the accompanying consolidated statements of operations. During the fourth quarter of 2017, Quanta recorded an impairment charge of $1.1 million related to a customer relationship intangible asset, which primarily resulted from a strategic decision to restructure a business within a reporting unit in the Oil and Gas Infrastructure Services Division. During the fourth quarter of 2015, Quanta recorded an impairment charge of $12.1 million related to customer relationship, trade name and non-compete agreement intangible assets, which primarily resulted from lower levels of expected activity in the U.S. Gulf of Mexico and, to a lesser extent, the extended low commodity price environment for certain directional drilling operations in Australia. The two reporting units impacted also had related goodwill impairments, as discussed above, and are in Quanta’s Oil and Gas Infrastructure Services Division.
Investments in Affiliates and Other Entities	Investments in Affiliates and Other Entities In the normal course of business, Quanta enters into various types of investment arrangements, each having unique terms and conditions. These investments may include equity interests held by Quanta in business entities, including general or limited partnerships, contractual joint ventures, or other forms of equity or profit participation. These investments may also include Quanta’s participation in different financing structures, such as the extension of loans to project specific entities, the acquisition of convertible notes issued by project specific entities, or other strategic financing arrangements. Quanta also enters into strategic partnerships with customers and infrastructure investors to provide fully integrated infrastructure services on certain projects, including planning and feasibility analyses, engineering, design, procurement, construction and project operation and maintenance. These projects include public-private partnerships, private infrastructure projects and concessions, along with build, own, operate and transfer and build-to-suit arrangements. As part of this strategy, during the year ended December 31, 2017, Quanta formed a partnership with select investors that provides up to $1.0 billion of capital, including approximately $80.0 million from Quanta, available to invest in certain of these infrastructure projects through August 2024. Wholly owned subsidiaries of Quanta serve as the general partner of this partnership and as a separately operated registered investment adviser that manages the invested capital. Quanta determines whether investments involve a variable interest entity (VIE) based on the characteristics of the subject entity. If the entity is determined to be a VIE, then management determines if Quanta is the primary beneficiary of the entity and whether or not consolidation of the VIE is required. The primary beneficiary consolidating the VIE must normally have both (i) the power to direct the activities that most significantly affect the VIE’s economic performance and (ii) the obligation to absorb significant losses of or the right to receive significant benefits from the VIE. When Quanta is deemed to be the primary beneficiary, the VIE is consolidated and the other party’s equity interest in the VIE is accounted for as a non-controlling interest. In cases where Quanta determines that it has an undivided interest in the assets, liabilities, revenues and profits of an unincorporated VIE (e.g., a general partnership interest), such amounts are consolidated on a basis proportional to Quanta’s ownership interest in the unincorporated entity. Investments in entities of which Quanta is not the primary beneficiary, but over which Quanta has the ability to exercise significant influence, are accounted for using the equity method of accounting. Quanta’s share of net income or losses from unconsolidated equity investments is reported as equity in earnings (losses) of unconsolidated affiliates, which is included in “Other income (expense)” in the accompanying consolidated statements of operations. Equity investments are reviewed for impairment by assessing whether any decline in the fair value of the investment below the carrying amount is other than temporary. In making this determination, factors such as the ability to recover the carrying amount of the investment and the inability of the investee to sustain an earnings capacity are evaluated in determining whether a loss in value should be recognized. Any impairment losses related to investments would be recognized in equity in earnings (losses) of unconsolidated affiliates. Equity method investments are carried at original cost and are included in “Other assets, net” in Quanta’s consolidated balance sheets and are adjusted for Quanta’s proportionate share of the investees’ income, losses and distributions. Quanta has a minority ownership interest in a limited partnership that was selected during 2014 to build, own and operate a new electric transmission line and two substations in Alberta, Canada. The limited partnership contracted with a Quanta subsidiary to perform the engineering, procurement and construction (EPC) services for the project, and the Quanta subsidiary recognizes revenue and related cost of services as performance progresses on the project. However, due to Quanta’s ownership interest, a proportional amount of the EPC profit is deferred until the electric transmission line and related substations are constructed and ownership of the assets is deemed to be transferred to the third party customer. The profit deferral has been recorded as a decrease to the equity method investment included in “Other assets, net” in the accompanying consolidated balance sheets and as a component of equity in earnings (losses) of unconsolidated affiliates, which is included in “Other income (expense)” in the accompanying consolidated statements of operations. See Notes 11 and 15 for additional disclosures related to investments.
Revenue Recognition	Revenue Recognition Quanta provides its services pursuant to master service agreements, repair and maintenance contracts and fixed price and non-fixed price installation contracts. Pricing under these contracts may be competitive unit price, cost-plus/hourly (or time and materials basis) or fixed price (or lump sum basis), and the final terms and prices of these contracts are frequently negotiated with the customer. Under unit-based contracts, the utilization of an output-based measurement is appropriate for revenue recognition, and Quanta recognizes revenue as units are completed based on pricing established with the customer for each delivered unit, which best reflects the pattern in which the obligation to the customer is fulfilled. Under cost-plus/hourly and time and materials type contracts, Quanta recognizes revenue on an input basis, as labor hours are incurred and services are performed. Revenues from fixed price contracts are recognized using the percentage-of-completion method, measured by the percentage of costs incurred to date to total estimated costs for each contract. Such contracts provide that the customer accept completion of progress to date and compensate Quanta for services rendered, which may be measured in terms of units installed, hours expended, costs incurred to date compared to total estimated contract costs or some other measure of progress. Contract costs include all direct materials, labor and subcontract costs and those indirect costs related to contract performance, such as indirect labor, supplies, tools, repairs and depreciation costs. Much of the material associated with Quanta’s work is owner-furnished and is therefore not included in contract revenues and costs. The cost estimation process is based on professional knowledge and experience of Quanta’s engineers, project managers and financial professionals. Changes in job performance, job conditions and final contract settlements are factors that influence management’s assessment of contract value and estimated costs, and as a result, the profit recognized. As discussed in Note 3, Quanta will adopt new revenue recognition guidance using the modified retrospective transition method effective for the quarter ending March 31, 2018, applying the guidance to contracts with customers that were not substantially complete as of January 1, 2018 . Quanta’s financial results for reporting periods after January 1, 2018 will be presented under the new guidance, while financial results for prior periods will continue to be reported in accordance with the prior guidance and Quanta’s historical accounting policy. Quanta has substantially completed its evaluation of the impact of the new guidance on its contracts with customers, including identification of differences that will result from the new requirements. Based on this evaluation, Quanta estimates that the net cumulative adjustment to retained earnings from adoption as of January 1, 2018 , will be less than $10.0 million . With respect to ongoing revenues generated from master service agreements, repair and maintenance contracts and fixed price and non-fixed price installation contracts, Quanta does not anticipate any significant changes to the pattern of revenue recognition and does not believe that the guidance surrounding identification of contracts and performance obligations or measurement of variable consideration will have a material impact on the revenue recognition for these arrangements. Quanta expects its disclosures related to revenue recognition will expand to address new quantitative and qualitative requirements regarding the nature, amount and timing of revenue from contracts with customers and additional information related to contract assets and liabilities. Actual revenues and project costs can vary, sometimes substantially, from previous estimates due to changes in a variety of factors, including unforeseen or changed circumstances not included in Quanta’s cost estimates or covered by its contracts for which it cannot obtain adequate compensation or reimbursement. Some of them include concealed or unknown environmental conditions; changes in the cost of equipment, commodities, materials or labor; unanticipated costs or claims due to delays caused by customers or third parties; customer failure to provide required materials or equipment; errors in engineering, specifications or designs; project modifications or contract termination; weather conditions; and quality issues requiring rework or replacement. These factors, along with other risks inherent in performing fixed price contracts, may cause actual revenues and gross profits for a project to differ from previous estimates and could result in reduced profitability or losses on projects. Changes in these factors may result in revisions to costs and income, and their effects are recognized in the period in which the revisions are determined. These factors are routinely evaluated on a project-by-project basis throughout the project term, and the impact of any such revisions in management’s estimates of contract value, contract cost and contract profit are recorded as necessary in the period in which the revisions are determined. Provisions for losses on uncompleted contracts are made in the period in which such losses are determined to be probable and the amount can be reasonably estimated. Quanta’s operating results for the year ended December 31, 2017 were impacted by less than 5% as a result of aggregate changes in contract estimates related to projects that were in progress at December 31, 2016 . Quanta’s operating results for the year ended December 31, 2016 were impacted by less than 5% as a result of aggregate changes in contract estimates related to projects that were in progress at December 31, 2015 . However, operating results for the year ended December 31, 2016 included losses of $54.8 million on a power plant construction project in Alaska due to performance issues that increased the estimated costs of the project. This project was substantially completed during the fourth quarter of 2016. The losses on this project were partially offset by the aggregate positive impact of numerous individually immaterial changes in profitability generally due to better than expected performance for projects that were ongoing at December 31, 2015. Quanta’s operating results for the year ended December 31, 2015 were impacted by numerous individually immaterial changes in contract estimates related to projects that were in progress at December 31, 2014; however, the aggregate impact was less than 5% despite losses of $44.9 million recorded during 2015 on the same Alaska power plant construction project. The current asset “Costs and estimated earnings in excess of billings on uncompleted contracts” represents revenues recognized in excess of amounts billed for contracts accounted for under the percentage-of-completion method. The current liability “Billings in excess of costs and estimated earnings on uncompleted contracts” represents billings in excess of revenues recognized for contracts accounted for under the percentage-of-completion method. Quanta may incur costs subject to change orders, whether approved or unapproved by the customer, and/or claims related to certain contracts. Quanta determines the probability that such costs will be recovered based upon evidence such as past practices with the customer, specific discussions or preliminary negotiations with the customer or verbal approvals. Quanta treats items as costs of contract performance in the period incurred if it is not probable that the costs will be recovered or will recognize additional revenue if it is probable that the contract price will be adjusted and can be reliably estimated. As of December 31, 2017 and 2016 , Quanta recognized revenues of $144.0 million and $137.8 million related to change orders and/or claims that were in the process of being negotiated and approved in the normal course of business. These aggregate contract price adjustments represent management’s best estimate of additional contract revenues which have been earned and which management believes are probable of collection. The amounts ultimately realized by Quanta upon final acceptance by its customers could be higher or lower than such estimated amounts; however, such amounts cannot currently be estimated.
Income Taxes	Income Taxes Quanta follows the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are recorded for future tax consequences of temporary differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that are expected to be in effect when the underlying assets or liabilities are recovered or settled. Quanta regularly evaluates valuation allowances established for deferred tax assets for which future realization is uncertain, including in connection with changes in tax laws affecting these assets. The estimation of required valuation allowances includes estimates of future taxable income. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Quanta considers projected future taxable income and tax planning strategies in making this assessment. If actual future taxable income differs from these estimates, Quanta may not realize deferred tax assets to the extent estimated. Quanta records reserves for income taxes related to certain tax positions in those instances where Quanta considers it more likely than not that additional taxes may be due in excess of amounts reflected on income tax returns filed. When recording reserves for expected tax consequences of uncertain positions, Quanta assumes that taxing authorities have full knowledge of the position and all relevant facts. Quanta continually reviews exposure to additional tax obligations, and as further information is known or events occur, changes in tax reserves may be recorded. To the extent interest and penalties may be assessed by taxing authorities on any underpayment of income tax, such amounts have been accrued and included in the provision for income taxes. As of December 31, 2017 , the total amount of unrecognized tax benefits relating to uncertain tax positions was $36.2 million , an increase from December 31, 2016 of $1.0 million . This increase resulted primarily from a $7.0 million increase in reserves for uncertain tax positions to be taken for 2017 and a $2.2 million net increase for uncertain tax positions related to prior years, partially offset by an $8.3 million decrease in reserves for uncertain tax positions resulting from the expiration of statute of limitations periods. Although the Internal Revenue Service (IRS) completed its examination related to tax years 2010, 2011 and 2012 during the year ended December 31, 2016, certain subsidiaries remain under examination by various U.S. state, Canadian and other foreign tax authorities for multiple periods. Quanta believes it is reasonably possible that within the next 12 months unrecognized tax benefits may decrease by up to $13.7 million as a result of settlement of these examinations or as a result of the expiration of certain statute of limitations periods. U.S. federal and state and foreign income tax laws and regulations are voluminous and are often ambiguous. As such, Quanta is required to make many subjective assumptions and judgments regarding its tax positions that could materially affect amounts recognized in its future consolidated balance sheets, consolidated statements of operations and consolidated statements of comprehensive income. For example, the Tax Cuts and Jobs Act of 2017 (the Tax Act) significantly revised the U.S. corporate tax regime and resulted in a remeasurement of Quanta’s deferred tax assets and liabilities and is anticipated to significantly reduce its future effective tax rate. For additional information on the status of Quanta’s provisional analysis of the Tax Act, refer to Note 10 .
Earnings Per Share	Earnings Per Share Basic and diluted earnings per share attributable to common stock are computed using the weighted average number of common shares outstanding during the applicable period. Exchangeable shares that were issued pursuant to certain of Quanta’s historical acquisitions (as further discussed in Note 11), which are exchangeable on a one -for-one basis with shares of Quanta common stock, have been included in the calculation of weighted average shares outstanding for basic and diluted earnings per share attributable to common stock for the portion of the periods that they were outstanding. Additionally, unvested stock-based awards that contain non-forfeitable rights to dividends or dividend equivalents (participating) have been included in the calculation of basic and diluted earnings per share attributable to common stock for the portion of the periods that they were outstanding. Diluted earnings per share attributable to common stock is computed using the weighted average number of common shares outstanding during the period adjusted for all potentially dilutive common stock equivalents, except in cases where the effect of the common stock equivalents would be antidilutive.
Insurance	Insurance Quanta is insured for employer’s liability, workers’ compensation, auto liability and general liability claims. Under these programs, the deductible for employer’s liability is $1.0 million per occurrence, the deductible for workers’ compensation is $5.0 million per occurrence, and the deductibles for auto liability and general liability are $10.0 million per occurrence. Quanta manages and maintains a portion of its casualty risk through its wholly-owned captive insurance company, which insures all claims up to the amount of the applicable deductible of its third-party insurance programs. Quanta also has employee health care benefit plans for most employees not subject to collective bargaining agreements, of which the primary plan is subject to a deductible of $0.4 million per claimant per year. Losses under all of these insurance programs are accrued based upon Quanta’s estimate of the ultimate liability for claims reported and an estimate of claims incurred but not reported, with assistance from third-party actuaries. These insurance liabilities are difficult to assess and estimate due to unknown factors, including the severity of an injury, the extent of damage, the determination of Quanta’s liability in proportion to other parties and the number of incidents not reported. The accruals are based upon known facts and historical trends, and management believes such accruals are adequate.
Collective Bargaining Agreements	Collective Bargaining Agreements Some of Quanta’s operating units are parties to various collective bargaining agreements with unions that represent certain of their employees. The collective bargaining agreements expire at various times and have typically been renegotiated and renewed on terms similar to those in the expiring agreements. The agreements require the operating units to pay specified wages, provide certain benefits to their union employees and contribute certain amounts to multiemployer pension plans and employee benefit trusts. Quanta’s multiemployer pension plan contribution rates generally are specified in the collective bargaining agreements (usually on an annual basis), and contributions are made to the plans on a “pay-as-you-go” basis based on its union employee payrolls. The location and number of union employees that Quanta employs at any given time and the plans in which they may participate vary depending on the projects Quanta has ongoing at that time and the need for union resources in connection with those projects. Therefore, Quanta is unable to accurately predict the union employee payroll and the amount of the resulting multiemployer pension plan contribution obligation for future periods.
Stock-Based Compensation	Stock-Based Compensation Quanta recognizes compensation expense for restricted stock, restricted stock units (RSUs) and performance units to be settled in common stock based on the fair value of the awards, net of estimated forfeitures. The fair value of these awards is generally determined based on the number of shares or units granted and the closing price of Quanta’s common stock on the date of grant; however, the fair value of performance units with market-based metrics is determined using a Monte Carlo simulation valuation methodology. An estimate of future forfeitures, based on historical data, is utilized to determine the period expense. Such estimates are subject to change and may impact the value that will ultimately be recognized as compensation expense. The resulting compensation expense for performance unit and time-based RSU awards is recognized on a straight-line basis over the requisite service period, which is generally the vesting period, and the resulting compensation expense for performance-based RSU awards is recognized using the graded vesting method over the requisite service period. The compensation expense related to performance units can also vary from period to period based on changes in the total number of performance units that Quanta anticipates will vest. Payments made by Quanta to satisfy employee tax withholding obligations associated with awards settled in common stock are classified as financing cash flows. Compensation expense associated with liability-based awards, such as RSUs that are expected to or may settle in cash, is recognized based on a remeasurement of the fair value of the award at the end of each reporting period. Upon settlement, the holders receive for each RSU an amount in cash equal to the fair market value on the settlement date of one share of Quanta common stock, as specified in the applicable award agreement. For additional information on Quanta’s restricted stock, RSU, and performance unit awards, see Note 12.
Functional Currency and Translation of Financial Statements	Functional Currency and Translation of Financial Statements The U.S. dollar is the functional currency for the majority of Quanta’s operations, which are primarily located within the United States. The functional currency for Quanta’s foreign operations, which are primarily located in Canada, Australia and Latin America, is typically the currency of the country where the foreign operating unit is located and transacts the majority of its activities, including billings, financing, payroll and other expenditures. The treatment of foreign currency translation gains or losses is dependent upon management’s determination of the functional currency, and when preparing its consolidated financial statements, Quanta translates the financial statements of its foreign operating units from their functional currency into U.S. dollars. Statements of operations, comprehensive income and cash flows are translated at average monthly rates, while balance sheets are translated at month-end exchange rates. The translation of the balance sheet results in translation gains or losses, which are included as a separate component of equity under “Accumulated other comprehensive income (loss).” Gains and losses arising from transactions not denominated in functional currencies are included within “Other income (expense)” in the accompanying consolidated statements of operations.
Comprehensive Income	Comprehensive Income Components of comprehensive income include all changes in equity during a period except those resulting from changes in Quanta’s capital related accounts. Quanta records other comprehensive income (loss) for foreign currency translation adjustments related to its foreign operations and for other revenues, expenses, gains and losses that are included in comprehensive income but excluded from net income.
Litigation Costs and Reserves	Litigation Costs and Reserves Quanta records reserves when the likelihood of incurring a loss is probable and the amount of loss can be reasonably estimated. Costs incurred for litigation are expensed as incurred. Further details are presented in Note 15.
Fair Value Measurements	Fair Value Measurements For disclosure purposes, qualifying assets and liabilities are categorized into three broad levels based on the priority of the inputs used to determine their fair values. The fair value hierarchy gives the highest priority to quoted prices (unadjusted) in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). Certain assumptions and other information as they relate to these qualifying assets and liabilities are described below. Contingent Consideration Liabilities. As of December 31, 2017 and 2016 , financial instruments required to be measured at fair value on a recurring basis consisted primarily of Quanta’s liabilities related to contingent consideration associated with certain acquisitions, the payment of which is contingent upon the future financial performance of the acquired businesses and, if earned, would be payable to the former owners of the acquired businesses. The liabilities recorded represent the estimated fair values of future amounts payable to the former owners, and the fair values are estimated by management based on entity-specific assumptions that are evaluated on an ongoing basis. As of December 31, 2017 and 2016 , the aggregate fair value of these outstanding and unearned contingent consideration liabilities totaled $65.7 million and $19.5 million , which was included in “Insurance and other non-current liabilities” in the accompanying consolidated balance sheets. The fair values of each contingent consideration liability as of December 31, 2017 was determined using a Monte Carlo simulation valuation methodology based on probability-weighted financial performance projections and other inputs, including a discount rate and an expected volatility factor for each acquisition. The discount rates ranged from 0.9% to 2.3% depending on the settlement methods available and are generally based on a risk-free rate and/or Quanta’s cost of debt. The expected volatility factors ranged from 23.0% to 32.7% based on historical asset volatility of selected guideline public companies. The fair value determinations incorporate significant inputs not observable in the market. Accordingly, the level of inputs used for these fair value measurements is the lowest level (Level 3). Significant changes in any of these assumptions could result in a significantly higher or lower potential liability. Quanta expects a significant portion of these liabilities to be settled by late 2020 or early 2021. The majority of Quanta’s contingent consideration liabilities are subject to a maximum payment amount, and the aggregate maximum payout amount for these liabilities was $139.5 million as of December 31, 2017 . One contingent consideration liability is not subject to a maximum payout amount, and the fair value of that liability was $1.0 million as of December 31, 2017 . Quanta’s aggregate contingent consideration liabilities can change due to additional business acquisitions, payments to settle outstanding liabilities, changes in the fair value of amounts owed, and foreign currency translation gains or losses. During the years ended December 31, 2017 , 2016 and 2015 , acquisitions increased Quanta’s contingent consideration liabilities by $51.1 million , $18.7 million and $1.0 million . Quanta made no payments related to contingent consideration liabilities during the years ended December 31, 2017 and 2015 and a nominal payment during the year ended December 31, 2016 . During the year ended December 31, 2017 , Quanta recognized a decrease in the fair value of contingent consideration liabilities of $5.2 million . No changes in fair value of contingent consideration liabilities were recognized in 2016 and 2015 . Changes in fair value of contingent consideration liabilities are included in “Change in fair value of contingent consideration liabilities” on Quanta’s consolidated statements of operations. Goodwill and Other Intangible Assets. In connection with Quanta’s acquisitions, identifiable intangible assets acquired typically include goodwill, backlog, customer relationships, trade names, covenants not-to-compete, patented rights and developed technology. Quanta utilizes the fair value premise as the primary basis for its valuation procedures, which is a market-based approach to determine the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Quanta periodically engages the services of an independent valuation firm when a new business is acquired to assist management with this valuation process, including assistance with the selection of appropriate valuation methodologies and the development of market-based valuation assumptions. Based on these considerations, management utilizes various valuation methods, including an income approach, a market approach and a cost approach, to determine the fair value of intangible assets acquired based on the appropriateness of each method in relation to the type of asset being valued. The assumptions used in these valuation methods are analyzed and compared, where possible, to available market data, such as industry-based weighted average costs of capital and discount rates, trade name royalty rates, public company valuation multiples and recent market acquisition multiples. In accordance with its annual impairment test during the quarter ended December 31, 2017 , the carrying amounts of such assets, including goodwill, were compared to their fair values. The level of inputs used for these fair value measurements is the lowest level (Level 3). Quanta uses the assistance of third party specialists to develop valuation assumptions. Quanta believes that these valuation methods appropriately represent the methods that would be used by other market participants in determining fair value. Investments and Financial Instruments. Quanta also uses fair value measurements in connection with the valuation of its investments in private company equity interests and financial instruments. These valuations require significant management judgment due to the absence of quoted market prices, the inherent lack of liquidity and the long-term nature of such assets. Typically, the initial costs of these investments are considered to represent fair market value, as such amounts are negotiated between willing market participants. On a quarterly basis, Quanta performs an evaluation of its investments to determine if an other-than-temporary decline in the value of each investment has occurred and whether the recorded amount of each investment will be realizable. If an other-than-temporary decline in the value of an investment occurs, a fair value analysis would be performed to determine the degree to which the investment was impaired and a corresponding charge to earnings would be recorded during the period. These types of fair market value assessments are similar to other nonrecurring fair value measures used by Quanta, which include the use of significant judgment and available relevant market data. Such market data may include observations of the valuation of comparable companies, risk adjusted discount rates and an evaluation of the expected performance of the underlying portfolio asset, including historical and projected levels of profitability or cash flows. In addition, a variety of additional factors may be reviewed by management, including, but not limited to, contemporaneous financing and sales transactions with third parties, changes in market outlook and the third-party financing environment. Other. The carrying amounts of cash equivalents, accounts receivable and accounts payable and accrued expenses approximate fair value due to the short-term nature of these instruments. The carrying amount of variable rate debt also approximates fair value. All of Quanta’s cash equivalents were categorized as Level 1 assets at December 31, 2017 and 2016 , as all values were based on unadjusted quoted prices for identical assets in an active market that Quanta has the ability to access.
Adoption of New Accounting Pronouncements and Accounting Standards Not Yet Adopted	Adoption of New Accounting Pronouncements In July 2015 , the FASB issued an update that requires inventory to be measured at the lower of either cost or net realizable value. When evidence exists that the net realizable value of inventory is lower than its cost, the difference will be recognized as a loss in earnings in the period in which it occurs. Quanta adopted this guidance effective January 1, 2017 , and the adoption of the update did not have a significant impact on its consolidated financial statements or related disclosures. In March 2016 , the FASB issued an update that amends the accounting for share-based payments in several key areas, including the treatment and cash flow presentation of tax effects related to the settlement of share-based payments and the accounting for forfeitures of share-based awards. The new guidance requires companies with share-based payments to record all related tax effects at settlement (or expiration) through income tax expense on the statement of operations rather than through additional paid-in capital (APIC) within equity. This update also requires excess tax benefits to be classified as an operating activity on the statement of cash flows rather than classified as a financing activity and requires cash paid by an employer when withholding shares for the employee portion of taxes to be presented as a financing activity. The update also allows companies to either account for forfeitures of share-based payments as they occur or to estimate forfeitures. This guidance is required to be applied prospectively except for the classification of cash related to tax withholding, which requires retrospective application. Quanta adopted this guidance effective January 1, 2017 and will continue to estimate forfeitures of share-based payments. Quanta experienced increased volatility of income tax expense after adoption of this guidance and anticipates that trend to continue. During the year ended December 31, 2017 , Quanta recorded income tax benefits of $5.1 million related to the settlement of share-based awards. APIC was not adjusted for amounts recorded prior to 2017, and therefore Quanta’s retained earnings were not affected by the adoption of this guidance. Additionally, $8.3 million and $9.8 million were reclassified from operating activities to financing activities on the statements of cash flows for the years ended December 31, 2016 and 2015 associated with cash paid by Quanta to satisfy tax withholding obligations for share-settled awards. Further, the presentation of excess tax benefits on the statements of cash flows is now shown as cash flows from operating activities rather than in financing activities. The excess tax benefits reclassified to operating activities for each of the years ended December 31, 2016 and 2015 was $0.7 million . In October 2016 , the FASB issued an update that amends the consolidation guidance related to how a reporting entity that is the single decision maker of a VIE should treat indirect interests in the VIE held through related parties that are under common control with the reporting entity when determining whether it is the primary beneficiary of a VIE. A reporting entity has an indirect interest in a VIE if it has a direct interest in a related party that, in turn, has a direct interest in the VIE. Quanta adopted this guidance effective January 1, 2017 , and the adoption of the update did not have a significant impact on its consolidated financial statements or related disclosures. In January 2017 , the FASB issued an update intended to simplify the subsequent measurement of goodwill by eliminating the second step in the two-step goodwill impairment test. As permitted under this guidance, Quanta elected to adopt this guidance for its annual goodwill impairment test during the fourth quarter of 2017 (see Note 2 for further detail on this update and a description of the quantitative goodwill impairment test). Accounting Standards Not Yet Adopted To be adopted effective January 1, 2018: In May 2014 , the FASB issued an update that supersedes most current revenue recognition guidance, as well as certain cost recognition guidance. The update, together with other clarifying updates, requires that the recognition of revenue related to the transfer of goods or services to customers reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The update also requires new qualitative and quantitative disclosures about the nature, amount, timing and uncertainty of revenues and cash flows arising from customer contracts, including significant judgments and changes in judgments, information about contract balances and performance obligations, and assets recognized from costs incurred to obtain or fulfill a contract. The new guidance is effective for fiscal years beginning on or after December 15, 2017 and can be applied on a full retrospective or modified retrospective basis, whereby the entity records a cumulative effect of initially applying this update at the date of initial application. Quanta will adopt the new revenue recognition guidance using the modified retrospective transition method effective for the quarter ending March 31, 2018, applying the guidance to contracts that were not substantially complete as of January 1, 2018 . Quanta’s financial results for reporting periods after January 1, 2018 will be presented under the new guidance, while financial results for prior periods will continue to be reported in accordance with the prior guidance and Quanta’s historical accounting policy. Quanta has substantially completed its evaluation of the impact of the new guidance on its contracts with customers, including identification of differences that will result from the new requirements. Based on this evaluation, we estimate that the net cumulative adjustment to retained earnings from adoption as of January 1, 2018 , will be less than $10.0 million . With respect to ongoing revenues generated from master service agreements, repair and maintenance contracts and fixed price and non-fixed price installation contracts, Quanta does not anticipate any significant changes to the pattern of revenue recognition and does not believe that the guidance surrounding identification of contracts and performance obligations or measurement of variable consideration will have a material impact on the revenue recognition for these arrangements. Quanta expects its disclosures related to revenue recognition will expand to address new quantitative and qualitative requirements regarding the nature, amount and timing of revenue from contracts and additional information related to contract assets and liabilities. In January 2016 , the FASB issued an update that addresses certain aspects of recognition, measurement, presentation, and disclosure of financial instruments to provide users of financial statements with more decision-useful information. This update requires equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. However, an entity may choose to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. The new standard is effective for interim and annual periods beginning after December 15, 2017 , and Quanta will adopt the new standard effective January 1, 2018 . Quanta’s equity investments that are within the scope of this update do not have readily determinable fair values. Accordingly, Quanta intends to continue to measure these investments at cost less any impairments and will also consider changes resulting from any observable price changes as described above. The new standard is not expected to have a material impact on Quanta’s consolidated financial statements in the near-term based on the equity investments it held as of December 31, 2017 . In August 2016 , the FASB issued an update intended to standardize the classification of certain transactions on the statements of cash flows . These transactions include contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies and distributions received from equity method investments. The new standard is effective for interim and annual reporting periods beginning after December 15, 2017 and requires application using a retrospective transition method. Quanta will adopt this guidance effective January 1, 2018 and does not expect it to have a material impact on its consolidated financial statements. In October 2016 , the FASB issued an update that will require a reporting entity to recognize the tax expense from the sale of an asset in the seller’s tax jurisdiction when the transfer occurs, even though the pre-tax effects of that transaction are eliminated in consolidation. Any deferred tax asset that arises in the buyer’s jurisdiction would also be recognized at the time of the transfer. The new guidance will not apply to intra-entity transfers of inventory. The income tax consequences from the sale of inventory from one member of a consolidated entity to another will continue to be deferred until the inventory is sold to a third party. The new standard is effective for interim and annual reporting periods beginning after December 15, 2017 . The modified retrospective method will be required for transition to the new guidance, with a cumulative-effect adjustment recorded in retained earnings as of the beginning of the period of adoption, if applicable. Quanta will adopt this guidance effective January 1, 2018 and does not expect it to have a material impact on its consolidated financial statements. In November 2016 , the FASB issued an update intended to standardize the classification of restricted cash and cash equivalents transactions on the statement of cash flows . The new guidance requires net cash withdrawn from (deposited to) restricted cash to be removed from investing activities of continuing operations. Additionally, restricted cash balances for each period will be included with “Cash and cash equivalents” in order to obtain beginning and ending balances for consolidated statement of cash flow purposes, and any activity between “Cash and cash equivalents” and restricted cash will no longer be reported on Quanta’s consolidated statements of cash flows. The new standard is effective for interim and annual reporting periods beginning after December 15, 2017 . The retrospective transition method will be required for this new guidance. Quanta will adopt this guidance effective January 1, 2018 and does not expect it to have a material impact on its consolidated financial statements. In January 2017 , the FASB issued an update intended to clarify whether transactions should be accounted for as acquisitions or disposals of assets or business es. When substantially all of the fair value of the gross assets acquired or disposed of is concentrated in a single identifiable asset or group of similar identifiable assets, the asset or group is not a business. The update will require, among other things, that to be considered a business, a set of assets and activities must include, at a minimum, an input and a substantive process that together significantly contribute to the ability to create output. Additionally, the update removes the evaluation of whether a market participant could replace missing elements in order to consider the set of assets and activities a business, provides more stringent criteria for sets without outputs and narrows the definition of output. The update is effective for interim and annual reporting periods beginning after December 15, 2017 , and the prospective transition method will be required for this new guidance. Accordingly, Quanta will adopt this guidance effective January 1, 2018 and does not expect it to impact its consolidated financial statements prior to such date. In May 2017 , the FASB issued an update providing guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. A modification should be accounted for unless the following characteristics of the award are unchanged: the fair value, the vesting conditions and the classification as an equity instrument or a liability instrument. The update is effective for interim and annual periods beginning after December 15, 2017 and is required to be applied prospectively. Accordingly, Quanta will adopt this guidance effective January 1, 2018 and does not expect it to impact its consolidated financial statements prior to such date. To be adopted subsequent to January 1, 2018: In February 2016 , the FASB issued an update that requires companies to recognize on the balance sheet the contractual right to use assets and liabilities corresponding to the rights and obligations created by lease contracts. The new standard is effective for interim and annual periods beginning after December 15, 2018 . While Quanta continues to evaluate the effect of the standard on its consolidated financial statements, it is anticipated that the adoption of the standard will materially impact its consolidated balance sheets. Quanta will adopt this guidance by January 1, 2019 . In June 2016 , the FASB issued an update that will change the way companies measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The update will require companies to use an “expected loss” model for instruments measured at amortized cost and to record allowances for available-for-sale debt securities rather than reduce the carrying amounts. The update will also require disclosure of information regarding how a company developed its allowance, including changes in the factors that influenced management’s estimate of expected credit losses and the reasons for those changes. Companies will apply this standard’s provisions as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. The new standard is effective for interim and annual reporting periods beginning after December 15, 2019 . Quanta is currently evaluating the potential impact of this authoritative guidance on its consolidated financial statements and will adopt this guidance by January 1, 2020 . In August 2017 , the FASB issued an update which amends and simplifies existing guidance for presenting the economic effects of risk management activities in the financial statements. The update is effective for interim and annual periods beginning after December 15, 2018 . The amended presentation and disclosure guidance is required only prospectively, but certain amendments, if applicable, could require a cumulative-effect adjustment. Quanta is evaluating the impact of this new standard on its consolidated financial statements and will adopt the new standard by January 1, 2019 ; however, as of December 31, 2017 , Quanta had no hedging relationships outstanding.
Treasury Stock	Treasury Stock General Treasury stock is recorded at cost. Under Delaware corporate law, treasury stock is not counted for quorum purposes or entitled to vote. Shares withheld for tax withholding obligations Under the stock incentive plans described in Note 12, the tax withholding obligations of employees upon vesting of restricted stock, RSUs and performance units settled in common stock are typically satisfied by Quanta making such tax payments and withholding the number of vested shares having a value on the date of vesting equal to the tax withholding obligation. For the settlement of these employee tax liabilities, Quanta withheld 0.5 million shares of Quanta common stock during the year ended December 31, 2017 , with a total market value of $18.6 million , 0.4 million shares of Quanta common stock during the year ended December 31, 2016 with a total market value of $8.3 million , and 0.4 million shares of Quanta common stock during the year ended December 31, 2015 with a total market value of $10.4 million . These shares and the related costs to acquire them were accounted for as adjustments to the balance of treasury stock. Notional amounts recorded related to deferred compensation plans For RSUs and performance units that vest but the settlement of which is deferred under Quanta’s deferred compensation plans, Quanta records an amount to treasury stock and an offsetting amount to APIC. No shares are recorded as treasury stock at vesting as the shares of Quanta common stock associated with deferred equity awards are not issued. Upon settlement of the deferred equity awards and issuance of the associated Quanta common stock, the original accounting entry is reversed. The net amounts recorded to treasury stock related to the deferred compensation plans during the years ended December 31, 2017 , 2016 and 2015 were $2.6 million , $6.8 million and $6.6 million , respectively. An aggregate $16.9 million was included in treasury stock for notional amounts related to deferred compensation plans at December 31, 2017 . Retirement of Treasury Stock Effective December 1, 2016 , Quanta retired 84.8 million shares of treasury stock. These retired shares were restored to the status of authorized and unissued shares as permitted by Delaware law. The retired stock had a carrying amount of $1.95 billion . In accordance with Quanta’s policy, Quanta recorded the formal retirement of treasury stock by deducting the par value from common stock and the excess of cost over par value from APIC. Stock repurchases During the second quarter of 2017, Quanta’s board of directors approved a stock repurchase program that authorizes Quanta to purchase, from time to time through June 30, 2020, up to $300.0 million of its outstanding common stock (the 2017 Repurchase Program). Repurchases under the 2017 Repurchase Program can be made in open market and privately negotiated transactions. As of December 31, 2017 , Quanta had repurchased 1.4 million shares of its common stock at a cost of $50.0 million in the open market under the 2017 Repurchase Program. During the third quarter of 2015, Quanta’s board of directors approved a stock repurchase program that authorized Quanta to purchase, from time to time through February 28, 2017, up to $1.25 billion of its outstanding common stock (the 2015 Repurchase Program). During 2015, Quanta repurchased 19.2 million shares of its common stock at a cost of $449.9 million in the open market under the 2015 Repurchase Program. During the third quarter of 2015, Quanta also entered into an accelerated share repurchase arrangement (the ASR) to repurchase $750.0 million of its common stock under the 2015 Repurchase Program. Pursuant to the terms of the ASR, based on the final volume-weighted average share price during the term of the ASR, minus a discount and subject to other adjustments, Quanta paid $750.0 million to JPMorgan Chase Bank, National Association, London Branch (JPMorgan) and received 25.7 million shares of its common stock in the third quarter of 2015 and 9.4 million shares of its common stock in the second quarter of 2016. As a result, Quanta repurchased a total of 54.3 million shares of its common stock at a cost of $1.20 billion under the 2015 Repurchase Program prior to its termination on February 28, 2017. During the fourth quarter of 2013, Quanta’s board of directors approved a stock repurchase program authorizing Quanta to purchase, from time to time through December 31, 2016, up to $500 million of its outstanding common stock (the 2013 Repurchase Program). During the year ended December 31, 2015, Quanta repurchased 14.3 million shares of its common stock at a cost of $406.5 million in the open market and completed the 2013 Repurchase Program.
Segment Reporting	Quanta presents its operations under two reportable segments: (1) Electric Power Infrastructure Services and (2) Oil and Gas Infrastructure Services. This structure is generally based on the broad end-user markets for Quanta’s services. See Note 1 for additional information regarding Quanta’s reportable segments. Quanta’s segment results are derived from the types of services provided across its operating units in each of the end user markets described above. Quanta’s entrepreneurial business model allows each of its operating units to serve the same or similar customers and to provide a range of services across end user markets. Quanta’s operating units are organized into one of two internal divisions, namely, the Electric Power Infrastructure Services Division and the Oil and Gas Infrastructure Services Division. These internal divisions are closely aligned with the reportable segments and are based on their operating units’ predominant type of work. Reportable segment information, including revenues and operating income by type of work, is gathered from each operating unit for the purpose of evaluating segment performance in support of Quanta’s market strategies. These classifications of Quanta’s operating unit revenues by type of work for segment reporting purposes can at times require judgment on the part of management. Quanta’s operating units may perform joint projects for customers in multiple industries, deliver multiple types of services under a single customer contract or provide service across industries. For example, Quanta performs joint trenching projects to install distribution lines for electric power and natural gas customers. In addition, Quanta’s integrated operations and common administrative support at each of its operating units require that certain allocations be made to determine segment profitability, including allocations of shared and indirect costs, such as facility costs, indirect operating expenses including depreciation, and general and administrative costs. Corporate costs, such as payroll and benefits, employee travel expenses, facility costs, professional fees, acquisition costs and amortization related to intangible assets are not allocated.
Acquisitions	This allocation requires a significant use of estimates and is based on information that was available to management at the time these consolidated financial statements were prepared. Quanta uses a variety of information to estimate fair values, including quoted market prices, carrying values and valuation techniques such as discounted cash flows. Third-party appraisal firms are engaged to assist in fair value determination of fixed assets, intangible assets and certain other assets and liabilities when appropriate (in thousands).

Summary of Significant Accoun29

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Significant Estimates Used by Management in Determining Fair Values of Company's Reporting Units	The following table presents the significant estimates used by management in determining the fair values of Quanta’s reporting units at December 31, 2017 , 2016 and 2015 : 2017 2016 2015 Years of cash flows before terminal value 5 years 5 years 5 years Discount rates 12.0% to 14.0% 12.5% to 14.5% 12.0% to 16.0% EBITDA multiples 5.5 to 7.0 5.5 to 7.0 5.0 to 6.5 Weighting of three approaches: Discounted cash flows 70% 70% 70% Market multiple 15% 15% 15% Market capitalization 15% 15% 15%
Fair Value Measurement Inputs for Acquisition	The following table presents the significant estimates used by management in determining the fair values of customer relationships associated with acquisitions in the years ended December 31, 2017 , 2016 and 2015 : 2017 2016 2015 Discount rates 17% to 25% 20% to 23% 18% to 22% Customer attrition rates 15% to 78% 10% to 70% 14% to 70%

Discontinued Operations (Tables

Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Summary of Financial Information for Discontinued Operations	The following represents a reconciliation of the major classes of line items constituting income from discontinued operations primarily related to Quanta’s fiber optic licensing operations to the accompanying consolidated statements of operations (in thousands): Year Ended December 31, 2016 2015 Major classes of line items constituting pretax income from discontinued operations: Revenues $ — $ 59,998 Expenses: Cost of services (including depreciation) — 24,748 Selling, general and administrative expenses (980 ) 12,047 Amortization of intangible assets — 963 Other income (expense) items that are not major — 10 Net income before taxes of discontinued operations related to fiber optic licensing operations related to major classes of income before taxes 980 22,250 Pretax gain on the disposal of the fiber optic licensing operations — 271,833 Total pretax gain on fiber optic licensing operations 980 294,083 Provision for income taxes related to fiber optic licensing operations 667 103,462 Net income from discontinued operations related to fiber optic licensing operations 313 190,621 Net loss from discontinued operations related to telecommunication operations (655 ) — Net income (loss) from discontinued operations as presented in the accompanying consolidated statements of operations $ (342 ) $ 190,621

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Summary of Aggregate Consideration Paid or Payable and Allocation of Amounts to the Net Tangible and Identifiable Intangible Assets	This allocation requires a significant use of estimates and is based on information that was available to management at the time these consolidated financial statements were prepared. Quanta uses a variety of information to estimate fair values, including quoted market prices, carrying values and valuation techniques such as discounted cash flows. Third-party appraisal firms are engaged to assist in fair value determination of fixed assets, intangible assets and certain other assets and liabilities when appropriate (in thousands). 2017 2016 Stronghold Other Acquisitions All Acquisitions Consideration: Cash paid or payable $ 351,014 $ 11,904 $ 75,941 Value of Quanta common stock issued 81,337 8,267 1,508 Contingent consideration 51,084 — 18,683 Fair value of total consideration transferred or estimated to be transferred $ 483,435 $ 20,171 $ 96,132 Accounts receivable $ 77,478 $ 7,157 $ 14,414 Costs and estimated earnings in excess of billings on uncompleted contracts 11,913 193 1,237 Other current assets 20,914 170 8,582 Property and equipment 51,258 1,480 44,863 Other assets 1,513 12 2,553 Identifiable intangible assets 95,700 8,091 11,467 Current liabilities (71,835 ) (2,798 ) (12,097 ) Deferred tax liabilities, net — — (13,484 ) Other long-term liabilities (48 ) — (5,326 ) Total identifiable net assets 186,893 14,305 52,209 Goodwill 296,542 5,866 43,923 $ 483,435 $ 20,171 $ 96,132
Estimated Fair Values of Identifiable Intangible Assets and Related Weighted Average Amortization	The following table summarizes the estimated fair values of identifiable intangible assets for the 2017 acquisitions as of the acquisition dates and the related weighted average amortization periods by type (in thousands, except for weighted average amortization periods, which are in years). Estimated Weighted Average Fair Value Amortization Period in Years Customer relationships $ 76,213 6.8 Backlog 333 2.0 Trade names 18,815 15.0 Non-compete agreements 8,430 5.0 Total intangible assets subject to amortization acquired in 2017 acquisitions $ 103,791 8.1
Unaudited Supplemental Pro Forma Results of Operations	Future results may vary significantly from the results reflected in the following pro forma financial information because of future events and transactions, as well as other factors (in thousands, except per share amounts): Year Ended December 31, 2017 2016 2015 Revenues $ 9,712,820 $ 8,183,104 $ 7,770,744 Gross profit $ 1,301,322 $ 1,129,661 $ 956,925 Selling, general and administrative expenses $ 821,084 $ 734,900 $ 612,979 Amortization of intangible assets $ 40,356 $ 46,579 $ 39,947 Net income from continuing operations $ 320,768 $ 207,956 $ 136,608 Net income from continuing operations attributable to common stock $ 317,521 $ 206,241 $ 125,691 Earnings per share from continuing operations: Basic $ 2.01 $ 1.29 $ 0.64 Diluted $ 2.00 $ 1.29 $ 0.64

Goodwill and Other Intangible32

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Changes in Quanta's Goodwill	A summary of changes in Quanta’s goodwill is as follows (in thousands): Electric Power Infrastructure Services Division Oil and Gas Infrastructure Services Division Total Balance at December 31, 2015: Goodwill $ 1,226,245 $ 366,306 1,592,551 Accumulated impairment — (39,893 ) (39,893 ) 1,226,245 326,413 1,552,658 Goodwill recorded related to 2016 acquisitions 24,168 21,018 45,186 Purchase price allocation adjustments 229 (214 ) 15 Foreign currency translation adjustments 3,337 1,973 5,310 Balance at December 31, 2016: Goodwill 1,253,979 388,923 1,642,902 Accumulated impairment — (39,733 ) (39,733 ) 1,253,979 349,190 1,603,169 Goodwill recorded related to 2017 acquisitions 5,866 296,542 302,408 Purchase price allocation adjustments (619 ) (659 ) (1,278 ) Goodwill impairment during 2017 — (57,011 ) (57,011 ) Foreign currency translation adjustments 13,301 8,011 21,312 Balance at December 31, 2017: Goodwill 1,272,527 693,905 1,966,432 Accumulated impairment — (97,832 ) (97,832 ) $ 1,272,527 $ 596,073 $ 1,868,600
Other Intangible Assets	Quanta’s intangible assets subject to amortization and the remaining weighted average amortization periods related to such assets were as follows (in thousands except for weighted average amortization periods, which are in years): As of As of As of December 31, 2017 December 31, 2016 December 31, 2017 Intangible Assets Accumulated Amortization Intangible Assets, Net Intangible Assets Accumulated Amortization Intangible Assets, Net Remaining Weighted Average Amortization Period in Years Customer relationships $ 327,334 $ (137,333 ) $ 190,001 $ 244,329 $ (110,640 ) $ 133,689 7.3 Backlog 136,266 (135,847 ) 419 133,592 (132,441 ) 1,151 1.1 Trade names 74,797 (17,057 ) 57,740 54,723 (12,855 ) 41,868 16.2 Non-compete agreements 37,760 (27,659 ) 10,101 29,212 (25,546 ) 3,666 3.9 Patented rights and developed technology 22,529 (17,611 ) 4,918 22,480 (15,831 ) 6,649 3.4 Total intangible assets subject to amortization $ 598,686 $ (335,507 ) $ 263,179 $ 484,336 $ (297,313 ) $ 187,023 9.1
Estimated Future Aggregate Amortization Expense of Intangible Assets	The estimated future aggregate amortization expense of intangible assets subject to amortization as of December 31, 2017 is set forth below (in thousands): For the Fiscal Year Ending December 31, 2018 $ 39,188 2019 37,038 2020 35,639 2021 33,295 2022 29,764 Thereafter 88,255 Total $ 263,179

Per Share Information (Tables)

Per Share Information (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Basic and Diluted Earnings Per Share	The amounts used to compute the basic and diluted earnings per share attributable to common stock for the years ended December 31, 2017 , 2016 and 2015 are illustrated below (in thousands): Year Ended December 31, 2017 2016 2015 Amounts attributable to common stock: Net income from continuing operations $ 314,978 $ 198,725 $ 120,286 Net income (loss) from discontinued operations — (342 ) 190,621 Net income attributable to common stock $ 314,978 $ 198,383 $ 310,907 Weighted average shares: Weighted average shares outstanding for basic earnings per share attributable to common stock 156,124 157,287 195,113 Effect of dilutive unvested non-participating stock-based awards 1,031 1 7 Weighted average shares outstanding for diluted earnings per share attributable to common stock 157,155 157,288 195,120

Detail of Certain Balance She34

Detail of Certain Balance Sheet Accounts (Tables)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Current and Long-Term Allowance for Doubtful Accounts	Activity in Quanta’s current and long-term allowance for doubtful accounts consisted of the following (in thousands): December 31, 2017 2016 Balance at beginning of year $ 2,752 $ 5,226 Charged to bad debt expense (recoveries of bad debt expense) 87 (543 ) Deductions for uncollectible receivables written off (recoveries of uncollectible receivables) 1,626 (1,931 ) Balance at end of year $ 4,465 $ 2,752
Schedule of Contracts in Progress	Contracts in progress were as follows (in thousands): December 31, 2017 2016 Costs incurred on contracts in progress $ 7,912,999 $ 6,687,484 Estimated earnings, net of estimated losses 1,092,303 766,560 9,005,302 7,454,044 Less — Billings to date (8,941,397 ) (7,255,582 ) $ 63,905 $ 198,462 Costs and estimated earnings in excess of billings on uncompleted contracts $ 497,292 $ 473,308 Less — Billings in excess of costs and estimated earnings on uncompleted contracts (433,387 ) (274,846 ) $ 63,905 $ 198,462
Schedule of Property and Equipment	Property and equipment consisted of the following (in thousands): Estimated Useful December 31, Lives in Years 2017 2016 Land N/A $ 48,832 $ 45,919 Buildings and leasehold improvements 5-30 155,628 137,515 Operating equipment and vehicles 5-25 1,834,715 1,634,850 Office equipment, furniture and fixtures and information technology systems 3-10 170,115 145,174 Construction work in progress N/A 60,587 73,461 2,269,877 2,036,919 Less — Accumulated depreciation and amortization (981,275 ) (862,825 ) Property and equipment, net $ 1,288,602 $ 1,174,094
Schedule of Accounts Payable and Accrued Expenses	Accounts payable and accrued expenses consisted of the following (in thousands): December 31, 2017 2016 Accounts payable, trade $ 632,931 $ 529,608 Accrued compensation and related expenses 225,193 194,056 Accrued insurance, current portion 64,112 60,880 Deferred revenues, current portion 15,967 15,512 Income and franchise taxes payable 19,635 40,765 Other accrued expenses 99,622 81,998 $ 1,057,460 $ 922,819

Debt Obligations (Tables)

Debt Obligations (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Long-term Debt Obligations	Quanta’s long-term debt obligations consisted of the following (in thousands): December 31, 2017 2016 Borrowings under credit facility $ 668,427 $ 351,341 Other long-term debt, interest rates ranging from 2.4% to 4.3% 1,810 3,305 Capital leases, interest rates ranging from 2.5% to 3.8% 1,704 3,744 Total long-term debt obligations 671,941 358,390 Less — Current maturities of long-term debt 1,220 4,828 Total long-term debt obligations, net of current maturities $ 670,721 $ 353,562
Current Maturities of Long-Term Debt and Short-Term Debt	Quanta’s current maturities of long-term debt and short-term debt consisted of the following (in thousands): December 31, 2017 2016 Short-term debt $ — $ 2,735 Current maturities of long-term debt 1,220 4,828 Current maturities of long-term debt and short-term debt $ 1,220 $ 7,563
Information on Borrowings under Current and Prior Credit Facility and Applicable Interest Rates	Borrowings under the credit facility and the applicable interest rates during the years ended December 31, 2017 , 2016 and 2015 were as follows (dollars in thousands): Year Ended December 31, 2017 2016 2015 Maximum amount outstanding under the credit facility during the period $ 917,895 $ 518,607 $ 606,753 Average daily amount outstanding under the credit facility $ 613,130 $ 458,908 $ 258,815 Weighted-average interest rate 2.7 % 2.1 % 1.8 %

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Components of Income (Loss) Before Income Taxes	The components of income (loss) from continuing operations before income taxes were as follows (in thousands): Year Ended December 31, 2017 2016 2015 Income (loss) from continuing operations before income taxes: Domestic $ 291,031 $ 349,959 $ 244,955 Foreign 62,726 (42,273 ) (16,280 ) Total $ 353,757 $ 307,686 $ 228,675
Provision for Income Taxes	The components of the provision for income taxes for continuing operations were as follows (in thousands): Year Ended December 31, 2017 2016 2015 Current: Federal $ 44,695 $ 106,316 $ 85,830 State 301 11,549 9,783 Foreign 22,666 5,076 21,262 Total current tax provision 67,662 122,941 116,875 Deferred: Federal (36,915 ) (264 ) (5,247 ) State 14,951 (923 ) 917 Foreign (10,166 ) (14,508 ) (15,073 ) Total deferred tax benefit (32,130 ) (15,695 ) (19,403 ) Total provision for income taxes from continuing operations $ 35,532 $ 107,246 $ 97,472
Effective Income Tax Rate Reconciliation	The actual income tax provision differed from the income tax provision computed by applying the U.S. federal statutory corporate rate to income from continuing operations before provision for income taxes as follows (in thousands): Year Ended December 31, 2017 2016 2015 Provision at the statutory rate $ 123,815 $ 107,690 $ 80,036 Increases (decreases) resulting from — Tax Cuts and Jobs Act (70,129 ) — — State taxes 17,920 6,479 7,241 Foreign taxes (16,958 ) 1,860 1,239 Contingency reserves, net 3,651 (13,540 ) 4,438 Production activity deduction (1,504 ) (8,586 ) (6,871 ) Employee per diems, meals and entertainment 13,605 8,764 8,727 Taxes on unincorporated joint ventures (1,354 ) (656 ) (3,838 ) Asset impairments — 1,909 7,047 Entity restructuring and recapitalization efforts (26,668 ) — — Equity compensation (5,095 ) — — Other (1,751 ) 3,326 (547 ) Total provision for income taxes from continuing operations $ 35,532 $ 107,246 $ 97,472
Deferred Tax Assets and Liabilities and Net Deferred Income Tax Assets and Liabilities	The tax effects of these temporary differences, representing deferred tax assets and liabilities, result principally from the following (in thousands): December 31, 2017 2016 Deferred income tax liabilities: Property and equipment $ (161,491 ) $ (214,902 ) Goodwill (49,407 ) (83,097 ) Other intangibles (26,676 ) (33,566 ) Customer holdbacks (36,218 ) (16,424 ) Other book/tax accounting method differences (15,154 ) (24,817 ) Total deferred income tax liabilities (288,946 ) (372,806 ) Deferred income tax assets: Accruals and reserves 21,419 21,681 Accrued insurance — 79,630 Stock and incentive compensation and pension withdrawal liabilities 17,676 58,744 Net operating loss carryforwards 62,925 37,362 Tax credits 48,516 1,613 Other 4,747 5,933 Subtotal 155,283 204,963 Valuation allowance (19,328 ) (14,991 ) Total deferred income tax assets 135,955 189,972 Total net deferred income tax liabilities $ (152,991 ) $ (182,834 ) The net deferred income tax assets and liabilities were comprised of the following in the accompanying consolidated balance sheets (in thousands): December 31, 2017 2016 Deferred income taxes: Assets $ 26,390 $ 10,000 Liabilities (179,381 ) (192,834 ) Total net deferred income tax liabilities $ (152,991 ) $ (182,834 )
Reconciliation of Unrecognized Tax Benefit	A reconciliation of unrecognized tax benefit balances is as follows (in thousands): December 31, 2017 2016 2015 Balance at beginning of year $ 35,240 $ 54,541 $ 50,668 Additions based on tax positions related to the current year 7,040 4,227 5,340 Additions for tax positions of prior years 3,372 2,048 292 Reductions for tax positions of prior years (1,171 ) (1,948 ) (132 ) Reductions for audit settlements — (180 ) (1,345 ) Reductions resulting from a lapse of the applicable statute of limitations periods (8,252 ) (23,448 ) (282 ) Balance at end of year $ 36,229 $ 35,240 $ 54,541
Balances of Unrecognized Tax Benefits	The balances of unrecognized tax benefits, the amount of related interest and penalties and what Quanta believes to be the range of reasonably possible changes in the next 12 months are as follows (in thousands): December 31, 2017 2016 2015 Unrecognized tax benefits $ 36,229 $ 35,240 $ 54,541 Portion that, if recognized, would reduce tax expense and effective tax rate 35,561 33,128 48,312 Accrued interest on unrecognized tax benefits 5,368 5,539 8,750 Accrued penalties on unrecognized tax benefits 631 650 673 Reasonably possible reduction to the balance of unrecognized tax benefits in succeeding 12 months $0 to $13,655 $0 to $12,332 $0 to $27,485 Portion that, if recognized, would reduce tax expense and effective tax rate $0 to $12,483 $0 to $10,983 $0 to $24,009

Equity-Based Compensation (Tabl

Equity-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Restricted Stock and RSU to be Settled in Common Stock Activity	A summary of the activity for RSUs to be settled in common stock for the year ended December 31, 2017 is as follows (shares in thousands): Shares Weighted Average Grant Date Fair Value (Per share) Unvested at December 31, 2016 2,711 $25.45 Granted 1,459 $37.06 Vested (1,489 ) $28.03 Forfeited (81 ) $27.58 Unvested at December 31, 2017 2,600 $30.42
Grant Date Fair Value for Awards of Performance Units Inputs	The grant date fair value for awards of performance units with market-based metrics, which were granted in the year ended December 31, 2017 , was based on a fair value as determined using a Monte Carlo simulation valuation methodology using the following key inputs: Valuation date stock price based on the March 22, 2017 closing stock price $36.31 Expected volatility 36.00 % Risk-free interest rate 1.46 % Term in years 2.78

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Summary of Plan Information Relating to Participation in Multiemployer Pension Plans	Information has been presented separately for individually significant plans, based on PPA funding status classification, and in the aggregate for all other plans. Employee Identification Number/ Pension Plan Number PPA Zone Status Subject to Financial Improve- ment/ Reha- bilitation Plan Contributions (in thousands) Sur-charge Imposed Expiration Date of Collective Bargaining Agreement Fund 2017 2016 2017 2016 2015 National Electrical Benefit Fund 53-0181657-001 Green Green No $ 29,161 $ 22,912 $ 21,200 No Varies through May 2022 Pipeline Industry Pension Fund 73-6146433-001 Green Green No 13,585 6,954 6,087 No Varies through May 2020 Central Pension Fund of the IUOE & Participating Employers 36-6052390-001 Green Green No 12,176 5,668 5,677 No Varies through December 2020 Teamsters National Pipe Line Pension Plan 46-1102851-001 Green Green No 3,602 1,661 1,343 No Varies through December 2020 Laborers Pension Trust Fund for Northern California 94-6277608-001 Yellow Yellow Yes 3,387 3,805 2,603 Yes Varies through May 2020 Eighth District Electrical Pension Fund 84-6100393-001 Green Green No 3,208 3,089 2,544 No Varies through December 2020 Laborers National Pension Fund 75-1280827-001 Green Green No 3,049 1,358 7,671 No Varies through December 2020 Alaska Electrical Pension Plan 92-6005171-001 Green Green No 2,143 2,701 639 No Varies through December 2019 Operating Engineers Local 324 Pension Fund 38-1900637-001 Red Red Yes 1,969 1,291 1,231 Yes Varies through December 2020 OE Pension Trust Fund 94-6090764-001 Red Red Yes 1,703 1,508 1,264 Yes Varies through June 2020 Plumbers and Pipefitters National Pension Fund 52-6152779-001 Yellow Yellow Yes 1,273 1,666 850 No Varies through March 2021 Alaska Laborers - Employers Retirement Fund 91-6028298-001 Yellow Yellow Yes 536 1,216 181 No December 2018 Laborers District Council of W PA Pension Fund 25-6135576-001 Red Red Yes 418 876 21 Yes May 2018 Alaska Teamster Employer Pension Plan 92-6003463-024 Red Red Yes 255 659 513 Yes December 2018 Midwest Operating Engineers Pension Trust Fund 36-6140097-001 Yellow Yellow Yes 106 793 3,294 Yes June 2019 All other plans - U.S. 24,234 28,516 20,594 All other plans - Canada (1) 9,277 562 1,303 Total $ 110,082 $ 85,235 $ 77,015 (1) Multiemployer defined benefit pension plans in Canada are not subject to the reporting requirements under the PPA. Accordingly, certain information was not publicly available. Quanta’s contributions to the following individually significant plans were five percent or more of the total contributions to these plans for the periods indicated based on the Forms 5500 for these plans for the years ended December 31, 2016 and 2015 . Forms 5500 were not yet available for these plans for the year ended December 31, 2017 . Pension Fund Plan Years in which Quanta Contributions Were Five Percent or More of Total Plan Contributions Pipeline Industry Pension Fund 2016 and 2015 Eighth District Electrical Pension Fund 2016 and 2015 Local 697 IBEW and Electrical Industry Pension Fund 2016 and 2015 Local Union No. 9 IBEW and Outside Contractors Pension Fund 2016 and 2015 Alaska Plumbing and Pipefitting Industry Pension Fund 2016 and 2015 Teamsters National Pipe Line Pension Plan 2016 and 2015 Alaska Electrical Pension Plan 2016 IBEW Local 456 Pension Plan 2016 Michigan Electrical Employees’ Pension Plan 2016 Laborers National Pension Fund 2015 Michigan Upper Peninsula Intrl Brotherhood of Elec Workers Pension Plan 2015

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Minimum Lease Payments	The following schedule shows the future minimum lease payments under these leases as of December 31, 2017 (in thousands): Operating Leases Year Ending December 31: 2018 $ 115,985 2019 75,556 2020 49,287 2021 28,422 2022 15,883 Thereafter 30,871 Total minimum lease payments $ 316,004

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Summarized Financial Information	Summarized financial information for Quanta’s reportable segments is presented in the following table (in thousands): Year Ended December 31, 2017 2016 2015 Revenues: Electric Power Infrastructure Services $ 5,599,836 $ 4,850,495 $ 4,937,289 Oil and Gas Infrastructure Services 3,866,642 2,800,824 2,635,147 Consolidated $ 9,466,478 $ 7,651,319 $ 7,572,436 Operating income (loss) : Electric Power Infrastructure Services $ 518,130 $ 395,745 $ 362,328 Oil and Gas Infrastructure Services 184,083 149,502 142,929 Corporate and non-allocated costs (323,364 ) (224,434 ) (267,754 ) Consolidated $ 378,849 $ 320,813 $ 237,503 Depreciation: Electric Power Infrastructure Services $ 91,708 $ 91,269 $ 89,150 Oil and Gas Infrastructure Services 76,355 67,374 65,315 Corporate and non-allocated costs 15,745 11,597 8,380 Consolidated $ 183,808 $ 170,240 $ 162,845

Supplemental Cash Flow Inform41

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Schedule of Effect of Changes in Operating Assets and Liabilities, Net Of Non-Cash Transactions, On Cash Flows From Operating Activities of Continuing Operations	The net effect of changes in operating assets and liabilities, net of non-cash transactions, on cash flows from operating activities of continuing operations is as follows (in thousands): Year Ended December 31, 2017 2016 2015 Accounts and notes receivable $ (425,313 ) $ 144,877 $ 150,470 Costs and estimated earnings in excess of billings on uncompleted contracts 15,999 (152,702 ) (49,358 ) Inventories 14,110 (9,905 ) (33,524 ) Prepaid expenses and other current assets (32,079 ) 25,133 5,899 Accounts payable and accrued expenses and other non-current liabilities 29,722 81,792 7,311 Billings in excess of costs and estimated earnings on uncompleted contracts 139,114 (124,680 ) 153,017 Other, net 17,267 (13,743 ) (11,707 ) Net change in operating assets and liabilities, net of non-cash transactions $ (241,180 ) $ (49,228 ) $ 222,108
Schedule of Additional Supplemental Cash Flow Information	Additional supplemental cash flow information is as follows (in thousands): Year Ended December 31, 2017 2016 2015 Cash (paid) received during the period for - Interest paid related to continuing operations $ (19,373 ) $ (12,828 ) $ (7,087 ) Income taxes paid related to continuing operations $ (112,335 ) $ (121,662 ) $ (130,921 ) Income taxes paid related to discontinued operations $ — $ (7,260 ) $ (144,076 ) Income tax refunds related to continuing operations $ 9,845 $ 7,548 $ 23,788

Quarterly Financial Data (Una42

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Consolidated Operating Results by Quarter	The table below sets forth the unaudited consolidated operating results by quarter for the years ended December 31, 2017 and 2016 (in thousands, except per share information). For the Three Months Ended March 31, June 30, September 30, December 31, 2017: Revenues $ 2,178,170 $ 2,200,374 $ 2,609,307 $ 2,478,627 Gross profit 266,188 302,165 350,631 322,876 Net income 48,440 64,360 89,849 115,576 Net income attributable to common stock 48,267 63,837 89,313 113,561 Net income from continuing operations attributable to common stock 48,267 63,837 89,313 113,561 Basic earnings per share from continuing operations attributable to common stock $ 0.31 $ 0.41 $ 0.57 $ 0.72 Diluted earnings per share from continuing operations attributable to common stock $ 0.31 $ 0.41 $ 0.56 $ 0.72 2016: Revenues $ 1,713,737 $ 1,792,430 $ 2,042,186 $ 2,102,966 Gross profit 203,313 200,217 302,582 307,688 Net income 20,859 16,729 74,152 88,358 Net income attributable to common stock 20,496 16,562 73,742 87,583 Net income from continuing operations attributable to common stock 20,496 16,562 73,137 88,530 Basic earnings per share from continuing operations attributable to common stock $ 0.13 $ 0.11 $ 0.47 $ 0.57 Diluted earnings per share from continuing operations attributable to common stock $ 0.13 $ 0.11 $ 0.47 $ 0.57

Business and Organization (Deta

Business and Organization (Detail) $ in Millions	Aug. 04, 2015USD ($)	Sep. 30, 2015USD ($)	Dec. 31, 2017Segment	Dec. 31, 2016Acquisition	Dec. 31, 2015Acquisition
Organization And Description Of Business [Line Items]
Number of reportable segments | Segment			2
Acquisitions 2,016
Organization And Description Of Business [Line Items]
Number of business acquisitions | Acquisition				5
Acquisitions 2,015
Organization And Description Of Business [Line Items]
Number of business acquisitions | Acquisition					11
Fiber Optic Licensing Division
Organization And Description Of Business [Line Items]
Sales price of fiber optic licensing operations	$ 1,000
Net cash proceeds from sale of fiber optic licensing operations	$ 848.2
Gain on sale, net of tax		$ 171

Summary of Significant Accoun44

Summary of Significant Accounting Policies - Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 138,285	$ 112,183	$ 128,771	$ 190,515
Cash equivalents	7,100	8,800
Domestic Bank Accounts
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	83,100	19,500
Foreign Bank Accounts
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	55,200	92,700
Investments In Joint Ventures
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	16,700	11,500
Domestic Joint Ventures
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 10,000	$ 10,000

Summary of Significant Accoun45

Summary of Significant Accounting Policies - Current and Long-Term Accounts and Notes Receivable and Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Allowances for doubtful accounts on current receivable	$ 4,465	$ 2,752
Current retainage balances	300,500	231,000
Non-current retainage balances	41,900	5,200
Unbilled receivables	$ 303,900	$ 206,800

Summary of Significant Accoun46

Summary of Significant Accounting Policies - Property and Equipment (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Depreciation expense related to property and equipment		$ 183,808	$ 170,240	$ 162,845
Accrued capital expenditures		$ 9,600	12,700
Impairment of long-lived assets to be disposed of	$ 8,000		$ 8,000
Impairment of long-lived assets held-for-use				$ 6,600

Summary of Significant Accoun47

Summary of Significant Accounting Policies - Debt Issuance Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Debt issuance costs related to amendment	$ 1,507	$ 0	$ 3,795
Capitalized debt issuance costs	12,900	11,400
Accumulated amortization of debt issuance costs	7,400	6,000
Amortization expense related to capitalized debt issuance costs	$ 1,321	$ 1,356	$ 1,251

Summary of Significant Accoun48

Summary of Significant Accounting Policies - Significant Estimates Used by Management in Determining Fair Values of Company's Reporting Units (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Years of cash flows before terminal value	5 years	5 years	5 years
Discounted cash flows	70.00%	70.00%	70.00%
Market multiple	15.00%	15.00%	15.00%
Market capitalization	15.00%	15.00%	15.00%
Minimum
Goodwill [Line Items]
Discount rates	12.00%	12.50%	12.00%
EBITDA multiples	5.5	5.5	5
Maximum
Goodwill [Line Items]
Discount rates	14.00%	14.50%	16.00%
EBITDA multiples	7	7	6.5

Summary of Significant Accoun49

Summary of Significant Accounting Policies - Goodwill and Other Intangible Assets (Detail) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2017USD ($)Reporting_Unit	Dec. 31, 2015USD ($)Reporting_Unit	Dec. 31, 2017USD ($)DivisionsReporting_Unit	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)Reporting_Unit
Goodwill And Intangible Assets [Line Items]
Number of internal divisions | Divisions			2
Decrease in fair value of reporting units considered for impairment calculation	10.00%		10.00%
Goodwill	$ 1,868,600	$ 1,552,658	$ 1,868,600	$ 1,603,169	$ 1,552,658
Intangible assets	263,179		263,179	187,023
Market capitalization	6,020,000		6,020,000
Stockholders' equity	$ 3,791,571		$ 3,791,571	$ 3,339,427
Number of reporting units impacted by impairment charge | Reporting_Unit	2	2	2		2
Non-cash charge for impairment of goodwill	$ 57,000	$ 39,800	$ 57,011
Intangible asset impairment charges	1,100	$ 12,100	$ 1,100		$ 12,100
Minimum
Goodwill And Intangible Assets [Line Items]
Reporting units growth rates			(14.00%)
Discount rates			17.00%	20.00%	18.00%
Customer attrition rates			15.00%	10.00%	14.00%
Maximum
Goodwill And Intangible Assets [Line Items]
Reporting units growth rates			17.00%
Discount rates			25.00%	23.00%	22.00%
Customer attrition rates			78.00%	70.00%	70.00%
Oil and Gas Infrastructure Division, Operating Units that have been Negatively Impacted by Various Factors
Goodwill And Intangible Assets [Line Items]
Goodwill	50,100		$ 50,100
Intangible assets	$ 14,700		$ 14,700

Summary of Significant Accoun50

Summary of Significant Accounting Policies - Investments in Affiliates and Other Entities (Details) - Scenario, Forecast - Capital for Infrastructure Projects $ in Millions	Aug. 31, 2024USD ($)
Other Commitments [Line Items]
Outstanding capital commitment	$ 80
Infrastructure Investors Partnership
Other Commitments [Line Items]
Outstanding capital commitment	$ 1,000

Summary of Significant Accoun51

Summary of Significant Accounting Policies - Revenue Recognition (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue Recognition [Line Items]
Cumulative adjustment to retained earnings (less than)	$ (2,191,059)	$ (1,876,081)
Change orders and/or claims	$ 144,000	$ 137,800
Maximum
Revenue Recognition [Line Items]
Percent aggregate change in contract estimates impact on operating results is less than this percentage	5.00%	5.00%	5.00%
Alaska Power Plant Construction Project
Revenue Recognition [Line Items]
Losses on contracts		$ 54,800	$ 44,900
Accounting Standards Update 2014-09 | Pro Forma
Revenue Recognition [Line Items]
Cumulative adjustment to retained earnings (less than)	$ 10,000

Summary of Significant Accoun52

Summary of Significant Accounting Policies - Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Examination [Line Items]
Total amount of unrecognized tax benefits relating to uncertain tax positions	$ 36,229	$ 35,240	$ 54,541	$ 50,668
Amount of unrecognized tax benefits increase	1,000
Unrecognized tax benefits, increase from current period tax positions	7,040	4,227	5,340
Unrecognized tax benefits, increase from prior year tax positions	2,200
Unrecognized tax benefits, decrease resulting from expiration of statute of limitations	8,252	23,448	282
Maximum
Income Tax Examination [Line Items]
Reasonably possible reduction to the balance of unrecognized tax benefits in succeeding 12 months	$ 13,655	$ 12,332	$ 27,485

Summary of Significant Accoun53

Summary of Significant Accounting Policies - Earnings Per Share (Detail)	12 Months Ended
	Dec. 31, 2017shares
Accounting Policies [Abstract]
Number of shares of Common stock received for each exchangeable share (in shares)	1

Summary of Significant Accoun54

Summary of Significant Accounting Policies - Insurance (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)
Accounting Policies [Abstract]
Employer's liability claims subject to deductible per occurrence	$ 1,000,000
Worker's compensation claims per occurrence	5,000,000
Auto liability insurance claims deductible	10,000,000
General liability insurance claims deductible	10,000,000
Employee health care benefit plans subject to deductible per claimant	$ 400,000

Summary of Significant Accoun55

Summary of Significant Accounting Policies - Stock-Based Compensation (Detail)	12 Months Ended
	Dec. 31, 2017shares
Restricted Stock Units to be Settled in Cash
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares that may be received by RSU holder (in shares)	1

Summary of Significant Accoun56

Summary of Significant Accounting Policies - Fair Value Measurements (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ 51,100,000	$ 18,700,000	$ 1,000,000
Acquisitions that have maximum payouts	139,500,000
Change in fair value of contingent consideration	5,171,000	0	$ 0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ 65,700,000	$ 19,500,000
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs discount rate	12.00%	12.50%	12.00%
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs discount rate	14.00%	14.50%	16.00%
Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, payments	$ 0		$ 0
Contingent Consideration | Minimum | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs discount rate	0.90%
Fair value inputs expected volatility rate	23.00%
Contingent Consideration | Maximum | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs discount rate	2.30%
Fair value inputs expected volatility rate	32.70%
Acquisition Without Maximum Earn-Out | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ 1,000,000
Acquisitions 2,016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration		$ 18,683,000
Acquisitions that have maximum payouts		$ 39,500,000

New Accounting Pronouncements (

New Accounting Pronouncements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income tax benefit related to the settlement of share-based awards during period	$ 5,100
Net cash provided by (used in) operating activities of continuing operations	372,475	$ 390,187	$ 628,649
Net cash provided (used in) financing activities of continuing operations	227,764	(133,836)	(1,227,844)
Cumulative adjustment to retained earnings (less than)	(2,191,059)	(1,876,081)
Accounting Standards Update 2016-09, Statutory Tax Withholding Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by (used in) operating activities of continuing operations		8,300	9,800
Net cash provided (used in) financing activities of continuing operations		(8,300)	(9,800)
Accounting Standards Update 2016-09, Excess Tax Benefit Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by (used in) operating activities of continuing operations		700	700
Net cash provided (used in) financing activities of continuing operations		$ (700)	$ (700)
Pro Forma | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment to retained earnings (less than)	$ 10,000

Discontinued Operations - Narra

Discontinued Operations - Narrative (Detail) - USD ($)	Aug. 04, 2015	Sep. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Fiber Optic Licensing Division
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales price of fiber optic licensing operations	$ 1,000,000,000
Net cash proceeds from sale of fiber optic licensing operations	$ 848,200,000
Gain on disposal of discontinued operations before taxes		$ 271,800,000	$ 0	$ 271,833,000
Tax amount from gain loss of disposal of discontinued operations		100,800,000
Gain on sale, net of tax		$ 171,000,000
Assets of fiber optic licensing operations			0		$ 0
Liabilities of discontinued operations			0		$ 0
Telecommunications
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Legal fees			1,000,000
Legal fees, net of tax impact			$ 700,000

Discontinued Operations - Summa

Discontinued Operations - Summary of Financial Information for Fiber Optic Licensing Operations (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Major classes of line items constituting pretax income from discontinued operations:
Net income (loss) from discontinued operations		$ 0	$ (342)	$ 190,621
Fiber Optic Licensing Division
Major classes of line items constituting pretax income from discontinued operations:
Revenues			0	59,998
Cost of services (including depreciation)			0	24,748
Selling, general and administrative expenses			(980)	12,047
Amortization of intangible assets			0	963
Other income (expense) items that are not major			0	10
Net income before taxes of discontinued operations related to fiber optic licensing operations related to major classes of income before taxes			980	22,250
Pretax gain on the disposal of the fiber optic licensing operations	$ 271,800		0	271,833
Total pretax gain on fiber optic licensing operations			980	294,083
Provision for income taxes related to fiber optic licensing operations			667	103,462
Net income (loss) from discontinued operations			313	190,621
Telecommunications
Major classes of line items constituting pretax income from discontinued operations:
Net income (loss) from discontinued operations			$ (655)	$ 0

Acquisitions - 2017 Acquisition

Acquisitions - 2017 Acquisitions (Detail) - USD ($) $ in Thousands	Jul. 20, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Contingent consideration, maximum		$ 139,500
Contingent consideration		51,100	$ 18,700	$ 1,000
Goodwill acquired		302,408	$ 45,186
Stronghold
Business Acquisition [Line Items]
Cash paid or payable	$ 351,014
Number of shares granted for acquired companies (in shares)	2,693,680
Value of Quanta common stock issued	$ 81,337
Contingent consideration, maximum	$ 100,000
Contingent consideration financial target term	3 years
Contingent consideration	$ 51,084
Goodwill acquired	$ 296,542
Acquisitions 2017, other than Stronghold
Business Acquisition [Line Items]
Cash paid or payable		$ 11,904
Number of shares granted for acquired companies (in shares)		288,666
Value of Quanta common stock issued		$ 8,267
Contingent consideration		0
Goodwill acquired		5,866
Acquisitions 2,017
Business Acquisition [Line Items]
Net tangible assets acquired		97,400
Other intangible assets acquired		103,800
Goodwill acquired		$ 302,400

Acquisitions - 2016 Acquisition

Acquisitions - 2016 Acquisitions (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)Acquisitionshares	Dec. 31, 2017USD ($)	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Contingent consideration, maximum		$ 139,500
Contingent consideration	$ 18,700	$ 51,100	$ 1,000
Acquisitions 2,016
Business Acquisition [Line Items]
Number of business acquisitions | Acquisition	5
Cash paid or payable	$ 75,941
Number of shares granted for acquired companies (in shares) | shares	70,840
Value of Quanta common stock issued	$ 1,508
Contingent consideration, maximum	39,500
Contingent consideration	$ 18,683
Acquisitions 2016 | Electric Power Infrastructure Services Business
Business Acquisition [Line Items]
Number of business acquisitions | Acquisition	4

Acquisitions - 2015 Acquisition

Acquisitions - 2015 Acquisitions (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)Acquisitionshares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Business Acquisition [Line Items]
Contingent consideration	$ 1	$ 51.1	$ 18.7
Acquisitions 2,015
Business Acquisition [Line Items]
Number of business acquisitions | Acquisition	11
Cash paid or payable	$ 110.6
Number of shares granted for acquired companies (in shares) | shares	461,037
Value of Quanta common stock issued	$ 10.1
Contingent consideration	$ 1
Acquisitions 2015 | Electric Power Infrastructure Services Business
Business Acquisition [Line Items]
Number of business acquisitions | Acquisition	8
Acquisitions 2015 | Oil and Gas Infrastructure Services Business
Business Acquisition [Line Items]
Number of business acquisitions | Acquisition	3

Acquisitions - Business Acquisi

Acquisitions - Business Acquisition Purchase Price Allocation Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Jul. 20, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Contingent consideration		$ 51,100	$ 18,700	$ 1,000
Goodwill		302,408	45,186
Stronghold
Business Acquisition [Line Items]
Cash paid or payable	$ 351,014
Value of Quanta common stock issued	81,337
Contingent consideration	51,084
Fair value of total consideration transferred or estimated to be transferred	483,435
Accounts receivable	77,478
Costs and estimated earnings in excess of billings on uncompleted contracts	11,913
Other current assets	20,914
Property and equipment	51,258
Other assets	1,513
Identifiable intangible assets	95,700
Current liabilities	(71,835)
Deferred tax liabilities, net	0
Other long-term liabilities	(48)
Total identifiable net assets	186,893
Goodwill	296,542
Fair value of total consideration transferred or estimated to be transferred	$ 483,435
Acquisitions 2017, other than Stronghold
Business Acquisition [Line Items]
Cash paid or payable		11,904
Value of Quanta common stock issued		8,267
Contingent consideration		0
Fair value of total consideration transferred or estimated to be transferred		20,171
Accounts receivable		7,157
Costs and estimated earnings in excess of billings on uncompleted contracts		193
Other current assets		170
Property and equipment		1,480
Other assets		12
Identifiable intangible assets		8,091
Current liabilities		(2,798)
Deferred tax liabilities, net		0
Other long-term liabilities		0
Total identifiable net assets		14,305
Goodwill		5,866
Fair value of total consideration transferred or estimated to be transferred		$ 20,171
Acquisitions 2,016
Business Acquisition [Line Items]
Cash paid or payable			75,941
Value of Quanta common stock issued			1,508
Contingent consideration			18,683
Fair value of total consideration transferred or estimated to be transferred			96,132
Accounts receivable			14,414
Costs and estimated earnings in excess of billings on uncompleted contracts			1,237
Other current assets			8,582
Property and equipment			44,863
Other assets			2,553
Identifiable intangible assets			11,467
Current liabilities			(12,097)
Deferred tax liabilities, net			(13,484)
Other long-term liabilities			(5,326)
Total identifiable net assets			52,209
Goodwill			43,923
Fair value of total consideration transferred or estimated to be transferred			$ 96,132

Acquisitions - 2017, 2016 and 2

Acquisitions - 2017, 2016 and 2015 Acquisitions (Detail) - USD ($) $ in Thousands

Jul. 20, 2017

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Business Acquisition [Line Items]

Goodwill acquired

$ 302,408

$ 45,186

Revenues

$ 2,478,627

$ 2,609,307

$ 2,200,374

$ 2,178,170

$ 2,102,966

$ 2,042,186

$ 1,792,430

$ 1,713,737

9,466,478

7,651,319

$ 7,572,436

Income (loss) from continuing operations before income taxes

353,757

307,686

228,675

Electric Power Division

Business Acquisition [Line Items]

Goodwill acquired

5,866

24,168

Oil And Gas Division

Business Acquisition [Line Items]

Goodwill acquired

296,542

21,018

Acquisitions 2017, other than Stronghold

Business Acquisition [Line Items]

Goodwill acquired

5,866

Acquisitions 2017, other than Stronghold | Electric Power Division

Business Acquisition [Line Items]

Goodwill acquired

5,900

Stronghold

Business Acquisition [Line Items]

Goodwill acquired

$ 296,542

Stronghold | Oil And Gas Division

Business Acquisition [Line Items]

Goodwill acquired

296,500

Acquisitions 2,016

Business Acquisition [Line Items]

Goodwill acquired

43,923

Goodwill expected to be deductible for income tax

2,000

2,000

Revenues

68,500

Income (loss) from continuing operations before income taxes

(5,600)

Acquisition costs

300

Acquisitions 2016 | Electric Power Division

Business Acquisition [Line Items]

Goodwill acquired

23,600

Acquisitions 2016 | Oil And Gas Division

Business Acquisition [Line Items]

Goodwill acquired

$ 20,300

Acquisitions 2,015

Business Acquisition [Line Items]

Revenues

104,600

Income (loss) from continuing operations before income taxes

300

Acquisition costs

3,600

Acquisitions 2015 | Electric Power Division

Business Acquisition [Line Items]

Goodwill acquired

31,500

Acquisitions 2015 | Oil And Gas Division

Business Acquisition [Line Items]

Goodwill acquired

$ 20,400

Acquisitions 2,017

Business Acquisition [Line Items]

Goodwill acquired

302,400

Goodwill expected to be deductible for income tax

$ 302,400

302,400

Revenues

207,400

Income (loss) from continuing operations before income taxes

(8,100)

Acquisition costs

$ 5,400

Acquisitions - Estimated Fair V

Acquisitions - Estimated Fair Values of Identifiable Intangible Assets and Related Weighted Average Amortization (Detail) - Acquisitions $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Finite-Lived Intangible Assets [Line Items]
Estimated fair value at acquisition date	$ 103,791
Weighted average amortization period at acquisition dates (in years)	8 years 1 month
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Estimated fair value at acquisition date	$ 76,213
Weighted average amortization period at acquisition dates (in years)	6 years 9 months 18 days
Backlog
Finite-Lived Intangible Assets [Line Items]
Estimated fair value at acquisition date	$ 333
Weighted average amortization period at acquisition dates (in years)	2 years
Trade names
Finite-Lived Intangible Assets [Line Items]
Estimated fair value at acquisition date	$ 18,815
Weighted average amortization period at acquisition dates (in years)	15 years
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Estimated fair value at acquisition date	$ 8,430
Weighted average amortization period at acquisition dates (in years)	5 years

Acquisitions - Unaudited Supple

Acquisitions - Unaudited Supplemental Pro Forma Results of Operations (Detail) - Acquisitions - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Revenues	$ 9,712,820	$ 8,183,104	$ 7,770,744
Gross profit	1,301,322	1,129,661	956,925
Selling, general and administrative expenses	821,084	734,900	612,979
Amortization of intangible assets	40,356	46,579	39,947
Net income from continuing operations	320,768	207,956	136,608
Net income from continuing operations attributable to common stock	$ 317,521	$ 206,241	$ 125,691
Earnings per share from continuing operations - basic (in usd per share)	$ 2.01	$ 1.29	$ 0.64
Earnings per share from continuing operations - diluted (in usd per share)	$ 2	$ 1.29	$ 0.64

Goodwill and Other Intangible67

Goodwill and Other Intangible Assets - Summary of Changes in Quanta's Goodwill (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Goodwill gross, beginning balance			$ 1,642,902	$ 1,592,551
Accumulated impairment, beginning balance			(39,733)	(39,893)
Goodwill net, beginning balance			1,603,169	1,552,658
Goodwill acquired			302,408	45,186
Purchase price allocation adjustments			(1,278)	15
Goodwill impairments	$ (57,000)	$ (39,800)	(57,011)
Foreign currency translation adjustments			21,312	5,310
Goodwill gross, ending balance	1,966,432	1,592,551	1,966,432	1,642,902
Accumulated impairment, ending balance	(97,832)	(39,893)	(97,832)	(39,733)
Goodwill net, ending balance	1,868,600	1,552,658	1,868,600	1,603,169
Electric Power Infrastructure Services Division
Goodwill [Roll Forward]
Goodwill gross, beginning balance			1,253,979	1,226,245
Accumulated impairment, beginning balance			0	0
Goodwill net, beginning balance			1,253,979	1,226,245
Goodwill acquired			5,866	24,168
Purchase price allocation adjustments			(619)	229
Goodwill impairments			0
Foreign currency translation adjustments			13,301	3,337
Goodwill gross, ending balance	1,272,527	1,226,245	1,272,527	1,253,979
Accumulated impairment, ending balance	0	0	0	0
Goodwill net, ending balance	1,272,527	1,226,245	1,272,527	1,253,979
Oil and Gas Infrastructure Services Division
Goodwill [Roll Forward]
Goodwill gross, beginning balance			388,923	366,306
Accumulated impairment, beginning balance			(39,733)	(39,893)
Goodwill net, beginning balance			349,190	326,413
Goodwill acquired			296,542	21,018
Purchase price allocation adjustments			(659)	(214)
Goodwill impairments			(57,011)
Foreign currency translation adjustments			8,011	1,973
Goodwill gross, ending balance	693,905	366,306	693,905	388,923
Accumulated impairment, ending balance	(97,832)	(39,893)	(97,832)	(39,733)
Goodwill net, ending balance	$ 596,073	$ 326,413	$ 596,073	$ 349,190

Goodwill and Other Intangible68

Goodwill and Other Intangible Assets - Other Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 598,686	$ 484,336
Accumulated Amortization	(335,507)	(297,313)
Intangible Assets, Net	$ 263,179	187,023
Remaining Weighted Average Amortization Period in Years	9 years 1 month 6 days
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 327,334	244,329
Accumulated Amortization	(137,333)	(110,640)
Intangible Assets, Net	$ 190,001	133,689
Remaining Weighted Average Amortization Period in Years	7 years 3 months 24 days
Backlog
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 136,266	133,592
Accumulated Amortization	(135,847)	(132,441)
Intangible Assets, Net	$ 419	1,151
Remaining Weighted Average Amortization Period in Years	1 year 1 month 3 days
Trade names
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 74,797	54,723
Accumulated Amortization	(17,057)	(12,855)
Intangible Assets, Net	$ 57,740	41,868
Remaining Weighted Average Amortization Period in Years	16 years 2 months 12 days
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 37,760	29,212
Accumulated Amortization	(27,659)	(25,546)
Intangible Assets, Net	$ 10,101	3,666
Remaining Weighted Average Amortization Period in Years	3 years 10 months 24 days
Patented rights and developed technology
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 22,529	22,480
Accumulated Amortization	(17,611)	(15,831)
Intangible Assets, Net	$ 4,918	$ 6,649
Remaining Weighted Average Amortization Period in Years	3 years 4 months 24 days

Goodwill and Other Intangible69

Goodwill and Other Intangible Assets - Narrative (Detail) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2017USD ($)Reporting_Unit	Dec. 31, 2015USD ($)Reporting_Unit	Dec. 31, 2017USD ($)Reporting_Unit	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)Reporting_Unit
Goodwill and Intangible Assets Disclosure [Abstract]
Number of reporting units impacted by impairment charge | Reporting_Unit	2	2	2		2
Amortization of intangible assets			$ 32,205	$ 31,685	$ 34,848
Intangible asset impairment charges	$ 1,100	$ 12,100	$ 1,100		$ 12,100

Goodwill and Other Intangible70

Goodwill and Other Intangible Assets - Estimated Future Aggregate Amortization Expense of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
2,018	$ 39,188
2,019	37,038
2,020	35,639
2,021	33,295
2,022	29,764
Thereafter	88,255
Intangible Assets, Net	$ 263,179	$ 187,023

Per Share Information - Basic a

Per Share Information - Basic and Diluted Earnings Per Share (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amounts attributable to common stock:
Net income from continuing operations	$ 113,561	$ 89,313	$ 63,837	$ 48,267	$ 88,530	$ 73,137	$ 16,562	$ 20,496	$ 314,978	$ 198,725	$ 120,286
Net income (loss) from discontinued operations									0	(342)	190,621
Net income attributable to common stock	$ 113,561	$ 89,313	$ 63,837	$ 48,267	$ 87,583	$ 73,742	$ 16,562	$ 20,496	$ 314,978	$ 198,383	$ 310,907
Weighted average shares:
Weighted average shares outstanding for basic earnings per share attributable to common stock (in shares)									156,124,000	157,287,000	195,113,000
Effect of dilutive unvested non-participating stock-based awards (in shares)									1,031,000	1,000	7,000
Weighted average shares outstanding for diluted earnings per share attributable to common stock (in shares)									157,155,000	157,288,000	195,120,000
Number of shares of Common stock received for each exchangeable share (in shares)									1

Detail of Certain Balance She72

Detail of Certain Balance Sheet Accounts - Current and Long-Term Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance at beginning of year	$ 2,752	$ 5,226
Charged to bad debt expense (recoveries of bad debt expense)	87	(543)	$ 224
Deductions for uncollectible receivables written off (recoveries of uncollectible receivables)	1,626	(1,931)
Balance at end of year	$ 4,465	$ 2,752	$ 5,226

Detail of Certain Balance She73

Detail of Certain Balance Sheet Accounts - Contracts in Progress (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Costs incurred on contracts in progress	$ 7,912,999	$ 6,687,484
Estimated earnings, net of estimated losses	1,092,303	766,560
Cost and estimated earnings, total	9,005,302	7,454,044
Less — Billings to date	(8,941,397)	(7,255,582)
Cost and estimated earnings, net	63,905	198,462
Costs and estimated earnings in excess of billings on uncompleted contracts	497,292	473,308
Less — Billings in excess of costs and estimated earnings on uncompleted contracts	$ (433,387)	$ (274,846)

Detail of Certain Balance She74

Detail of Certain Balance Sheet Accounts - Property and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Land	$ 48,832	$ 45,919
Buildings and leasehold improvements	155,628	137,515
Operating equipment and vehicles	1,834,715	1,634,850
Office equipment, furniture and fixtures and information technology systems	170,115	145,174
Construction work in progress	60,587	73,461
Property and equipment, gross	2,269,877	2,036,919
Less — Accumulated depreciation and amortization	(981,275)	(862,825)
Property and equipment, net	$ 1,288,602	$ 1,174,094
Minimum | Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated Useful Lives in Years	5 years
Minimum | Operating equipment and vehicles
Property, Plant and Equipment [Line Items]
Estimated Useful Lives in Years	5 years
Minimum | Office equipment, furniture and fixtures and information technology systems
Property, Plant and Equipment [Line Items]
Estimated Useful Lives in Years	3 years
Maximum | Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated Useful Lives in Years	30 years
Maximum | Operating equipment and vehicles
Property, Plant and Equipment [Line Items]
Estimated Useful Lives in Years	25 years
Maximum | Office equipment, furniture and fixtures and information technology systems
Property, Plant and Equipment [Line Items]
Estimated Useful Lives in Years	10 years

Detail of Certain Balance She75

Detail of Certain Balance Sheet Accounts - Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accounts payable, trade	$ 632,931	$ 529,608
Accrued compensation and related expenses	225,193	194,056
Accrued insurance, current portion	64,112	60,880
Deferred revenues, current portion	15,967	15,512
Income and franchise taxes payable	19,635	40,765
Other accrued expenses	99,622	81,998
Accounts payable and accrued expenses, total	$ 1,057,460	$ 922,819

Debt Obligations - Long-term De

Debt Obligations - Long-term Debt Obligations (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Borrowings under credit facility	$ 668,427	$ 351,341
Other long-term debt, interest rates ranging from 2.4% to 4.3%	1,810	3,305
Capital leases, interest rates ranging from 2.5% to 3.8%	1,704	3,744
Total long-term debt obligations	671,941	358,390
Less — Current maturities of long-term debt	1,220	4,828
Total long-term debt obligations, net of current maturities	$ 670,721	$ 353,562
Other Long Term Debt | Minimum
Debt Instrument [Line Items]
Capital leases and Other long-term debt interest rates	2.40%	2.40%
Other Long Term Debt | Maximum
Debt Instrument [Line Items]
Capital leases and Other long-term debt interest rates	4.30%	4.30%
Capital Lease Obligations | Minimum
Debt Instrument [Line Items]
Capital leases and Other long-term debt interest rates	2.50%	2.50%
Capital Lease Obligations | Maximum
Debt Instrument [Line Items]
Capital leases and Other long-term debt interest rates	3.80%	3.80%

Debt Obligations - Current Matu

Debt Obligations - Current Maturities of Long-Term Debt and Short-Term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Short-term debt	$ 0	$ 2,735
Current maturities of long-term debt	1,220	4,828
Current maturities of long-term debt and short-term debt	$ 1,220	$ 7,563

Debt Obligations - Credit Facil

Debt Obligations - Credit Facility - Amended and Restated Credit Agreement (Detail) - Current Credit Agreement	Dec. 18, 2015USD ($)
Line of Credit Facility [Line Items]
Senior secured revolving credit facility	$ 1,810,000,000
Option to increase revolving commitments under the credit agreement	400,000,000
Revolving Loans and Letter of Credit in Alternative Currencies
Line of Credit Facility [Line Items]
Senior secured revolving credit facility	600,000,000
U S Dollar | Swing Lines Loan
Line of Credit Facility [Line Items]
Senior secured revolving credit facility	100,000,000
Canadian Dollars | Swing Lines Loan
Line of Credit Facility [Line Items]
Senior secured revolving credit facility	50,000,000
Australian Dollars | Swing Lines Loan
Line of Credit Facility [Line Items]
Senior secured revolving credit facility	$ 30,000,000

Debt Obligations - Credit Fac79

Debt Obligations - Credit Facility - Current Borrowings (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Amount borrowed under the credit facility	$ 668,427	$ 351,341
Credit facility available for revolving loans or issuing new letters of credit	728,300
Letters Of Credit and Bank Guarantees
Line of Credit Facility [Line Items]
Letters of credit and bank guarantees under the credit facility	413,300
Letters Of Credit and Bank Guarantees | U S Dollar
Line of Credit Facility [Line Items]
Letters of credit and bank guarantees under the credit facility	228,600
Letters Of Credit and Bank Guarantees | Primarily Canadian and Australian dollars
Line of Credit Facility [Line Items]
Letters of credit and bank guarantees under the credit facility	184,700
Borrowings Under Credit Facility
Line of Credit Facility [Line Items]
Amount borrowed under the credit facility	668,400
Borrowings Under Credit Facility | U S Dollar
Line of Credit Facility [Line Items]
Amount borrowed under the credit facility	645,000
Borrowings Under Credit Facility | Australian Dollars
Line of Credit Facility [Line Items]
Amount borrowed under the credit facility	$ 23,400

Debt Obligations - Information

Debt Obligations - Information on Borrowings under Current and Prior Credit Facility and Applicable Interest Rates (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Maximum amount outstanding under the credit facility during the period	$ 917,895	$ 518,607	$ 606,753
Average daily amount outstanding under the credit facility	$ 613,130	$ 458,908	$ 258,815
Weighted-average interest rate	2.70%	2.10%	1.80%

Debt Obligations - Credit Fac81

Debt Obligations - Credit Facility - Terms under the Amended and Restated Credit Agreement (Detail) - Current Credit Agreement	Nov. 20, 2017USD ($)	Nov. 19, 2017
Line of Credit Facility [Line Items]
Reduction in Quanta's funded indebtedness reduced by cash and cash equivalents in excess of this amount	$ 25,000,000
Percentage of capital stock of direct foreign subsidiaries of wholly owned U.S. subsidiaries to secure credit agreement	65.00%
Maximum consolidated leverage ratio	3
Acquisition threshold for leverage ratio	$ 200,000,000
Maximum leverage ratio acquisition completed in current and two subsequent quarters	3.5
Minimum consolidated interest coverage ratio	3
Amount of availability under the credit agreement and/or cash and cash equivalents on hand that must be present to allow for cash payments of dividends and stock repurchases	$ 100,000,000
Cross default provisions with debt instruments exceeding this amount	$ 100,000,000
Minimum
Line of Credit Facility [Line Items]
Commitment fee	0.20%
Minimum | Standby Letters of Credit
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	1.125%	1.125%
Minimum | Performance Letters of Credit
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	0.675%	0.675%
Maximum
Line of Credit Facility [Line Items]
Commitment fee	0.40%
Maximum | Standby Letters of Credit
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	2.00%	2.125%
Maximum | Performance Letters of Credit
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	1.15%	1.275%
Excess of Eurocurrency Rate Applicable to Domestic Borrowings Only | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	1.125%	1.125%
Excess of Eurocurrency Rate Applicable to Domestic Borrowings Only | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	2.00%	2.125%
Excess of Base Rate Domestic Borrowings Only | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	0.125%	0.125%
Excess of Base Rate Domestic Borrowings Only | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	1.00%	1.125%
Excess of Euro Currency Rate of Credit Agreement for Foreign Borrowings | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	1.125%	1.125%
Excess of Euro Currency Rate of Credit Agreement for Foreign Borrowings | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	2.00%	2.125%
Excess of Federal Funds Rate
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	0.50%
Excess of Euro Currency Rate
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	1.00%

Debt Obligations - Other Facili

Debt Obligations - Other Facilities (Details) $ in Millions	Dec. 31, 2017USD ($)
Letters Of Credit and Bank Guarantees
Debt Instrument [Line Items]
Letters of credit and bank guarantees under the credit facility	$ 413.3
Other facilities
Debt Instrument [Line Items]
Bilateral credit agreements availability	50.2
Other facilities | Letters Of Credit and Bank Guarantees
Debt Instrument [Line Items]
Letters of credit and bank guarantees under the credit facility	$ 2.8

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Tax Act, one-time net tax benefits	$ 70,100
Tax Act, benefits associated with re-measurement of deferred tax assets and liabilities	85,300
Tax Act, transition tax expense on post-1986 earnings and profits of certain foreign subsidiaries	15,200
Tax Act, benefit associated with entity restructuring and recapitalization	26,700
Tax Act, expense associated with acceleration of certain deductions	8,500
Valuation allowance for deferred income tax assets	19,328	$ 14,991	$ 16,100
Change in total valuation allowance	4,300	(1,100)	3,100
Tax effect of state and foreign net operating loss carryforwards	62,925	37,362
2,018	200
2,019	100
2,020	1,900
2,021	100
2,022	200
Thereafter	65,400
Valuation allowance foreign and state net operating loss carryforwards	17,800
Reduction due to expiration of certain federal and state statutes of limitations	8,252	23,448	282
Interest and penalties expense (income) in the provision for income taxes	(200)	$ (3,200)	$ 2,400
Gross Amount Before Balance Sheet Presentation Netting
Income Taxes [Line Items]
Tax effect of state and foreign net operating loss carryforwards	$ 67,900

Income Taxes - Components of In

Income Taxes - Components of Income (Loss) Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income (loss) from continuing operations before income taxes:
Domestic	$ 291,031	$ 349,959	$ 244,955
Foreign	62,726	(42,273)	(16,280)
Income from continuing operations before income taxes	$ 353,757	$ 307,686	$ 228,675

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 44,695	$ 106,316	$ 85,830
State	301	11,549	9,783
Foreign	22,666	5,076	21,262
Total current tax provision	67,662	122,941	116,875
Deferred:
Federal	(36,915)	(264)	(5,247)
State	14,951	(923)	917
Foreign	(10,166)	(14,508)	(15,073)
Total deferred tax benefit	(32,130)	(15,695)	(19,403)
Total provision for income taxes from continuing operations	$ 35,532	$ 107,246	$ 97,472

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate Reconciliation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Provision at the statutory rate	$ 123,815	$ 107,690	$ 80,036
Increases (decreases) resulting from —
Tax Cuts and Jobs Act	(70,129)	0	0
State taxes	17,920	6,479	7,241
Foreign taxes	(16,958)	1,860	1,239
Contingency reserves, net	3,651	(13,540)	4,438
Production activity deduction	(1,504)	(8,586)	(6,871)
Employee per diems, meals and entertainment	13,605	8,764	8,727
Taxes on unincorporated joint ventures	(1,354)	(656)	(3,838)
Asset impairments	0	1,909	7,047
Entity restructuring and recapitalization efforts	(26,668)	0	0
Equity compensation	(5,095)	0	0
Other	(1,751)	3,326	(547)
Total provision for income taxes from continuing operations	$ 35,532	$ 107,246	$ 97,472

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred income tax liabilities:
Property and equipment	$ (161,491)	$ (214,902)
Goodwill	(49,407)	(83,097)
Other intangibles	(26,676)	(33,566)
Customer holdbacks	(36,218)	(16,424)
Other book/tax accounting method differences	(15,154)	(24,817)
Total deferred income tax liabilities	(288,946)	(372,806)
Deferred income tax assets:
Accruals and reserves	21,419	21,681
Accrued insurance	0	79,630
Stock and incentive compensation and pension withdrawal liabilities	17,676	58,744
Net operating loss carryforwards	62,925	37,362
Tax credits	48,516	1,613
Other	4,747	5,933
Subtotal	155,283	204,963
Valuation allowance	(19,328)	(14,991)	$ (16,100)
Total deferred income tax assets	135,955	189,972
Total net deferred income tax liabilities	$ (152,991)	$ (182,834)

Income Taxes - Net Deferred Inc

Income Taxes - Net Deferred Income Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred income taxes:
Assets	$ 26,390	$ 10,000
Liabilities	(179,381)	(192,834)
Total net deferred income tax liabilities	$ (152,991)	$ (182,834)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Unrecognized Tax Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 35,240	$ 54,541	$ 50,668
Additions based on tax positions related to the current year	7,040	4,227	5,340
Additions for tax positions of prior years	3,372	2,048	292
Reductions for tax positions of prior years	(1,171)	(1,948)	(132)
Reductions for audit settlements	0	(180)	(1,345)
Reductions resulting from a lapse of the applicable statute of limitations periods	(8,252)	(23,448)	(282)
Balance at end of year	$ 36,229	$ 35,240	$ 54,541

Income Taxes - Balances of Unre

Income Taxes - Balances of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Unrecognized tax benefits	$ 36,229	$ 35,240	$ 54,541	$ 50,668
Portion that, if recognized, would reduce tax expense and effective tax rate	35,561	33,128	48,312
Accrued interest on unrecognized tax benefits	5,368	5,539	8,750
Accrued penalties on unrecognized tax benefits	631	650	673
Minimum
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Reasonably possible reduction to the balance of unrecognized tax benefits in succeeding 12 months	0	0	0
Portion that, if recognized, would reduce tax expense and effective tax rate	0	0	0
Maximum
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Reasonably possible reduction to the balance of unrecognized tax benefits in succeeding 12 months	13,655	12,332	27,485
Portion that, if recognized, would reduce tax expense and effective tax rate	$ 12,483	$ 10,983	$ 24,009

Equity - Exchangeable Shares an

Equity - Exchangeable Shares and Series F and Series G Preferred Stock (Detail)	Oct. 06, 2017shares	Dec. 31, 2017Acquisitionshares	Dec. 31, 2016shares	Dec. 31, 2015shares	Oct. 05, 2017shares
Class of Stock [Line Items]
Number of shares of Common stock received for each exchangeable share (in shares)		1
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 (in shares)		50,000
Number of business acquisitions having issuances of preferred stock | Acquisition		2
Common stock, shares outstanding (in shares)		153,342,326	144,710,773
Series F Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)		0	1		1
Preferred stock, shares retired (in shares)	1	1
Preferred stock, shares outstanding (in shares)		0	1
Series G Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)		1	1
Preferred stock, shares outstanding (in shares)		1	1
Exchangeable Shares For Common Stock
Class of Stock [Line Items]
Exchangeable shares exchanged for common stock (in shares)		6,000,000	400,000	400,000
Exchangeable Shares
Class of Stock [Line Items]
Common stock, shares outstanding (in shares)		486,112	6,515,453
Exchangeable Shares Associated with Series G Preferred Stock
Class of Stock [Line Items]
Common stock, shares outstanding (in shares)		400,000

Equity - Treasury Stock (Detail

Equity - Treasury Stock (Detail) - USD ($)	Dec. 01, 2016	Jun. 30, 2016	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 28, 2017	Jun. 30, 2017	Dec. 31, 2013
Equity, Class of Treasury Stock [Line Items]
Value of treasury stock acquired, cost method				$ 50,000,000		$ 1,456,361,000
Treasury stock, value				85,451,000	$ 14,288,000
Retirement of treasury stock, shares (in shares)	84,800,000
Retirement of treasury stock, amount					0
Payments for repurchase of common stock				$ 50,000,000	$ 0	1,606,361,000
Accelerated stock repurchases settled at a later date						$ 150,000,000
2017 Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired (in shares)				1,382,292
Value of treasury stock acquired, cost method				$ 50,000,000
2017 Repurchase Program | Maximum
Equity, Class of Treasury Stock [Line Items]
Aggregate authorized amount of common stock to be repurchased								$ 300,000,000
2015 Repurchase Plan Open Market Purchases And Accelerated Share Repurchase Agreement
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired (in shares)							54,300,000
Value of treasury stock acquired, cost method							$ 1,200,000,000
2015 Repurchase Program | Maximum
Equity, Class of Treasury Stock [Line Items]
Aggregate authorized amount of common stock to be repurchased			$ 1,250,000,000
2015 Repurchase Program Open Market Purchases
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired (in shares)						19,200,000
Value of treasury stock acquired, cost method						$ 449,900,000
Accelerated Share Repurchase Agreement
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired (in shares)		9,400,000	25,700,000
Aggregate authorized amount of common stock to be repurchased			$ 750,000,000
Payments for repurchase of common stock			$ 750,000,000
2013 Repurchase Program | Maximum
Equity, Class of Treasury Stock [Line Items]
Aggregate authorized amount of common stock to be repurchased									$ 500,000,000
2013 Repurchase Program Open Market Repurchases
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired (in shares)						14,300,000
Value of treasury stock acquired, cost method						$ 406,500,000
Common Stock Withheld for Settlement of Employee Tax Liabilities
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired (in shares)				500,000	400,000	400,000
Value of treasury stock acquired, cost method				$ 18,600,000	$ 8,300,000	$ 10,400,000
Treasury Stock Associated with Deferred Compensation Plans
Equity, Class of Treasury Stock [Line Items]
Value of treasury stock acquired, cost method				2,600,000	6,800,000	6,600,000
Treasury stock, value				16,900,000
Treasury Stock
Equity, Class of Treasury Stock [Line Items]
Value of treasury stock acquired, cost method				$ 50,000,000		$ 1,456,361,000
Retirement of treasury stock, amount					$ 1,946,129,000

Equity - Non-controlling Intere

Equity - Non-controlling Interests (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Income attributable to non-controlling interests	$ 3,247	$ 1,715	$ 10,917
Carrying value of the investments held by Quanta in variable interest entities	7,800	3,300
Non-controlling interests	4,058	3,275
Distributions to non-controlling interests	2,001	$ 761
Net distributions to non-controlling interests			$ 18,915
Decrease in non-controlling interests from purchase of interests	$ 463

Equity-Based Compensation - Sto

Equity-Based Compensation - Stock Incentive Plans (Detail)	Dec. 31, 2017shares
2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares of common stock that may be issued	11,750,000

Equity-Based Compensation - Res

Equity-Based Compensation - Restricted Stock and RSUs to be Settled in Common Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash stock compensation expense	$ 46,448	$ 42,843	$ 36,939
Restricted Stock Units to be Settled in Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, shares (in shares)	1,459,000	1,800,000	1,300,000
Granted, weighted average grant date fair value, per share (in usd per share)	$ 37.06	$ 22.22	$ 27.64
Awards vested (in shares)	1,489,000
Outstanding stock value	2,600,000	2,711,000
Unrecognized compensation cost, related to unvested restricted stock, total	$ 38,200
Expected weighted average period to recognize compensation cost on RSUs to be settled in common stock (in years)	1 year 7 months 10 days
Restricted Stock and Restricted Stock Units to be Settled in Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vested (in shares)	1,500,000	1,400,000	1,300,000
Fair value of restricted stock, vested	$ 55,600	$ 28,900	$ 35,900
Non-cash stock compensation expense	$ 41,000	$ 39,600	$ 33,300
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding stock value	0
Share-based Compensation Award, Tranche One | Restricted Stock Units to be Settled in Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for RSUs to be settled in stock	2 years
Share-based Compensation Award, Tranche Two | Restricted Stock Units to be Settled in Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for RSUs to be settled in stock	3 years
Share-based Compensation Award, Tranche Three | Restricted Stock Units to be Settled in Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for RSUs to be settled in stock	5 years

Equity-Based Compensation - Sum

Equity-Based Compensation - Summary of Restricted Stock and RSU to be Settled in Common Stock Activity (Detail) - Restricted Stock and RSUs to be Settled in Common Stock - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shares
Unvested, shares, beginning of period (in shares)	2,711
Granted, shares (in shares)	1,459	1,800	1,300
Vested, shares (in shares)	(1,489)
Forfeited, shares (in shares)	(81)
Unvested, shares, end of period (in shares)	2,600	2,711
Weighted Average Grant Date Fair Value (Per share)
Unvested, weighted average grant date fair value, beginning of period (in usd per share)	$ 25.45
Granted, weighted average grant date fair value (in usd per share)	37.06	$ 22.22	$ 27.64
Vested, weighted average grant date fair value (in usd per share)	28.03
Forfeited, weighted average grant date fair value (in usd per share)	27.58
Unvested, weighted average grant date fair value, end of period (in usd per share)	$ 30.42	$ 25.45

Equity-Based Compensation - Per

Equity-Based Compensation - Performance Units to be Settled in Common Stock (Detail) - Performance Units - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Required performance period	3 years
Performance units granted (in shares)	300,000	300,000	200,000
Granted, weighted average grant date fair value, per share (in usd per share)	$ 17.63	$ 22.86	$ 28.16
Compensation costs	$ 5.4	$ 3.2	$ 3.6
Awards vested (in shares)	100,000	0	0
Number of common shares issued in connection with performance units (in shares)	100,000	0	0
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance units performance percentage	0.00%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance units performance percentage	200.00%

Equity-Based Compensation - Gra

Equity-Based Compensation - Grant Date Fair Value for Awards of Performance Units Inputs (Details) - Performance Units - $ / shares	12 Months Ended
	Dec. 31, 2017	Mar. 22, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share price (in usd per share)		$ 36.31
Expected volatility	36.00%
Risk-free interest rate	1.46%
Term in years	2 years 9 months 11 days

Equity-Based Compensation - RSU

Equity-Based Compensation - RSUs to be Settled in Cash (Detail) - Restricted Stock Units to be Settled in Cash - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares that may be received by RSU holder (in shares)	1
Compensation expense related to RSUs to be settled in cash	$ 8.1	$ 7	$ 4
Payments to settle liabilities under compensation plan	8.6	4.6	$ 4.2
Accrued liabilities under compensation plan	$ 4.6	$ 5.1
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for RSUs to be settled in cash	2 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for RSUs to be settled in cash	3 years

Employee Benefit Plans - Narrat

Employee Benefit Plans - Narrative (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer defined contribution and other benefit plan contributions other than MEP DBP	$ 110,082	$ 85,235	$ 77,015
Percentage of contribution by employer of each employee's contribution up to 3%	100.00%
Percentage of contribution by employer of each employee who contributes between 3% and 6%	50.00%
Contributions to Quanta 401(k) Plan	$ 26,300	21,900	17,700
Contributions to the deferred compensation plans	1,100	1,000	1,000
Deferred compensation obligations included in other long-term liabilities	30,100	19,100
Investments in company-owned life insurance policies	$ 28,700	17,900
Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of employee contribution, lower range	3.00%
Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of employee contribution, lower range	6.00%
Union Employees
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer defined contribution and other benefit plan contributions other than MEP DBP	$ 171,400	$ 139,300	$ 147,100

Employee Benefit Plans - Summar

Employee Benefit Plans - Summary of Plan Information Relating to Participation in Multiemployer Pension Plans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Multiemployer Plans [Line Items]
Contributions	$ 110,082	$ 85,235	$ 77,015
National Electrical Benefit Fund
Multiemployer Plans [Line Items]
Contributions	29,161	22,912	21,200
Pipeline Industry Pension Fund
Multiemployer Plans [Line Items]
Contributions	13,585	6,954	6,087
Central Pension Fund of the IUOE & Participating Employers
Multiemployer Plans [Line Items]
Contributions	12,176	5,668	5,677
Teamsters National Pipe Line Pension Plan
Multiemployer Plans [Line Items]
Contributions	3,602	1,661	1,343
Laborers Pension Trust Fund for Northern California
Multiemployer Plans [Line Items]
Contributions	3,387	3,805	2,603
Eighth District Electrical Pension Fund
Multiemployer Plans [Line Items]
Contributions	3,208	3,089	2,544
Laborers National Pension Fund
Multiemployer Plans [Line Items]
Contributions	3,049	1,358	7,671
Alaska Electrical Pension Plan
Multiemployer Plans [Line Items]
Contributions	2,143	2,701	639
Operating Engineers Local 324 Pension Fund
Multiemployer Plans [Line Items]
Contributions	1,969	1,291	1,231
OE Pension Trust Fund
Multiemployer Plans [Line Items]
Contributions	1,703	1,508	1,264
Plumbers and Pipefitters National Pension Fund
Multiemployer Plans [Line Items]
Contributions	1,273	1,666	850
Alaska Laborers - Employers Retirement Fund
Multiemployer Plans [Line Items]
Contributions	536	1,216	181
Laborers District Council of W PA Pension Fund
Multiemployer Plans [Line Items]
Contributions	418	876	21
Alaska Teamster Employer Pension Plan
Multiemployer Plans [Line Items]
Contributions	255	659	513
Midwest Operating Engineers Pension Trust Fund
Multiemployer Plans [Line Items]
Contributions	106	793	3,294
All other plans, US
Multiemployer Plans [Line Items]
Contributions	24,234	28,516	20,594
All other plans, Canada
Multiemployer Plans [Line Items]
Contributions	$ 9,277	$ 562	$ 1,303

Related Party Transactions - Na

Related Party Transactions - Narrative (Detail) - Affiliated Entity - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Lease agreement terms	5 years
Related party lease expenses	$ 12.3	$ 8.7	$ 10.6

Commitments and Contingencies -

Commitments and Contingencies - Investments in Affiliates and Other Entities (Detail) $ in Millions	39 Months Ended
	Dec. 31, 2017USD ($)	Aug. 31, 2024USD ($)	May 31, 2022USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2014kVsubstationkm
Other Commitments, Planned Oil and Gas Infrastructure Projects
Other Commitments [Line Items]
Outstanding capital commitment	$ 16.9
Scenario, Forecast | Other Commitments, Planned Oil and Gas Infrastructure Projects
Other Commitments [Line Items]
Outstanding capital commitment			$ 2.1		$ 14.8
Scenario, Forecast | Capital for Infrastructure Projects
Other Commitments [Line Items]
Outstanding capital commitment		$ 80
EPC Electric Transmission Project
Other Commitments [Line Items]
Length of electrical transmission line to be constructed under contract | km						500
Number of substations | substation						2
Voltage of substations | kV						500
Aggregate contributions to this unconsolidated affiliate	66.7
Proceeds from return of capital	$ 64.4
EPC Electric Transmission Project | Scenario, Forecast
Other Commitments [Line Items]
Outstanding capital commitment				$ 25.2
Infrastructure Investors Partnership | Scenario, Forecast | Capital for Infrastructure Projects
Other Commitments [Line Items]
Outstanding capital commitment		$ 1,000

Commitments and Contingencie104

Commitments and Contingencies - Minimum Lease Payments (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,018	$ 115,985
2,019	75,556
2,020	49,287
2,021	28,422
2,022	15,883
Thereafter	30,871
Total minimum lease payments	$ 316,004

Commitments and Contingencie105

Commitments and Contingencies - Leases (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Rent expense related to operating leases	$ 276.2	$ 242.3	$ 208.5
Residual value guarantees
Guarantor Obligations [Line Items]
Maximum guaranteed residual value	$ 626.8

Commitments and Contingencie106

Commitments and Contingencies - Contingent Consideration Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ 51.1	$ 18.7	$ 1
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ 65.7	$ 19.5

Commitments and Contingencie107

Commitments and Contingencies - Committed Expenditures (Detail) $ in Millions	Dec. 31, 2017USD ($)
Vehicle Fleet Committed Capital
Unrecorded Unconditional Purchase Obligation [Line Items]
Estimated committed capital in next fiscal year	$ 14.6

Commitments and Contingencie108

Commitments and Contingencies - Legal Proceedings (Detail) - Maximum - USD ($) $ in Millions	1 Months Ended
	Feb. 28, 2018	Dec. 31, 2017
Maurepas Project Dispute
Loss Contingencies [Line Items]
Reasonable possible loss		$ 22
Lorenzo Benton V Telecom Network Specialists Inc
Loss Contingencies [Line Items]
Reasonable possible loss		$ 11.1
Subsequent Event | Lorenzo Benton V Telecom Network Specialists Inc
Loss Contingencies [Line Items]
Damages sought	$ 11.1

Commitments and Contingencie109

Commitments and Contingencies - Concentrations of Credit Risk (Detail) - Electric Power Infrastructure Services Segment Customer One - Net Receivable Position - Customer Concentration Risk - Quanta's Electric Power Infrastructure Services Segment	12 Months Ended
	Dec. 31, 2016Customer
Concentration Risk [Line Items]
Number of customers representing ten percent or more of concentration risk	1
Concentration risk percentage	16.00%

Commitments and Contingencie110

Commitments and Contingencies - Insurance (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Commitment And Contingencies [Line Items]
Insurance and other non-current liabilities	$ 342,356	$ 259,733
Insurance Claims
Commitment And Contingencies [Line Items]
Gross amount accrued for insurance claims	254,700	218,200
Insurance and other non-current liabilities	200,000	162,000
Related insurance recoveries/receivables	50,400	8,700
Related insurance recoveries/receivables included in prepaid expenses and other current assets	400	400
Related insurance recoveries/receivables included in other assets net	$ 50,000	$ 8,300

Commitments and Contingencie111

Commitments and Contingencies - Letters of Credit (Detail) $ in Millions	Dec. 31, 2017USD ($)
Letters Of Credit and Bank Guarantees
Loss Contingencies [Line Items]
Letters of credit and bank guarantees under the credit facility	$ 413.3

Commitments and Contingencie112

Commitments and Contingencies - Performance Bonds and Parent Guarantees (Detail) - Performance Guarantee $ in Millions	Dec. 31, 2017USD ($)
Loss Contingencies [Line Items]
Total amount of outstanding performance bonds	$ 3,000
Estimate
Loss Contingencies [Line Items]
Estimated cost to complete bonded projects	$ 869

Commitments and Contingencie113

Commitments and Contingencies - Collective Bargaining Agreements (Detail) - Withdrawal from Multiemployer Defined Benefit Plan - Central States Plan - USD ($) $ in Millions	1 Months Ended	55 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Jan. 31, 2016	Jul. 31, 2014	Oct. 09, 2013
Loss Contingencies [Line Items]
Final settlement amount	$ 48.9	$ 48.9
Amount of withdrawal liability	44.1	44.1	$ 32.9	$ 39.6
Interest on assessed amount of withdrawal liability	4.8	4.8
Payment of withdrawal liability assessment amount	$ 25.5
Acquired Company
Loss Contingencies [Line Items]
Amount of withdrawal liability			$ 4.8		$ 4.8
Payment of withdrawal liability assessment amount		$ 4.2
Amount of withdrawal liability, amount suggested by Plan which is different than amount recorded by company					$ 6.9

Commitments and Contingencie114

Commitments and Contingencies - Indemnities (Detail) - Indemnification Agreement $ in Millions	Dec. 31, 2017USD ($)
Loss Contingencies [Line Items]
Pre-acquisition non-U.S.tax obligations and indemnification asset amount recorded	$ 11.4
Pre-acquisition non-U.S.tax obligations and indemnification liability amount recorded	$ 11.4

Segment Information - Narrative

Segment Information - Narrative (Detail) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)SegmentDivisions	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment									2
Number of internal divisions | Divisions									2
Revenues	$ 2,478,627	$ 2,609,307	$ 2,200,374	$ 2,178,170	$ 2,102,966	$ 2,042,186	$ 1,792,430	$ 1,713,737	$ 9,466,478	$ 7,651,319	$ 7,572,436
Property and equipment	1,288,602				1,174,094				1,288,602	1,174,094
Non-US
Segment Reporting Information [Line Items]
Revenues									2,480,000	1,590,000	$ 1,540,000
Property and equipment	$ 330,400				$ 320,700				$ 330,400	$ 320,700
Canada
Segment Reporting Information [Line Items]
Percentage of foreign revenues									79.00%	75.00%	85.00%

Segment Information - Summarize

Segment Information - Summarized Financial Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 2,478,627	$ 2,609,307	$ 2,200,374	$ 2,178,170	$ 2,102,966	$ 2,042,186	$ 1,792,430	$ 1,713,737	$ 9,466,478	$ 7,651,319	$ 7,572,436
Operating income (loss)									378,849	320,813	237,503
Depreciation									183,808	170,240	162,845
Operating Segments | Electric Power Infrastructure Services
Segment Reporting Information [Line Items]
Revenues									5,599,836	4,850,495	4,937,289
Operating income (loss)									518,130	395,745	362,328
Depreciation									91,708	91,269	89,150
Operating Segments | Oil and Gas Infrastructure Services
Segment Reporting Information [Line Items]
Revenues									3,866,642	2,800,824	2,635,147
Operating income (loss)									184,083	149,502	142,929
Depreciation									76,355	67,374	65,315
Consolidated
Segment Reporting Information [Line Items]
Operating income (loss)									(323,364)	(224,434)	(267,754)
Depreciation									$ 15,745	$ 11,597	$ 8,380

Supplemental Cash Flow Infor117

Supplemental Cash Flow Information - Schedule of Effect of Changes in Operating Assets and Liabilities, Net of Non-Cash Transactions, on Cash Flows from Operating Activities of Continuing Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Accounts and notes receivable	$ (425,313)	$ 144,877	$ 150,470
Costs and estimated earnings in excess of billings on uncompleted contracts	15,999	(152,702)	(49,358)
Inventories	14,110	(9,905)	(33,524)
Prepaid expenses and other current assets	(32,079)	25,133	5,899
Accounts payable and accrued expenses and other non-current liabilities	29,722	81,792	7,311
Billings in excess of costs and estimated earnings on uncompleted contracts	139,114	(124,680)	153,017
Other, net	17,267	(13,743)	(11,707)
Net change in operating assets and liabilities, net of non-cash transactions	$ (241,180)	$ (49,228)	$ 222,108

Supplemental Cash Flow Infor118

Supplemental Cash Flow Information - Schedule of Additional Supplemental Cash Flow Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash (paid) received during the period for -
Notes receivable exchanged	$ 7,100
Continuing Operations
Cash (paid) received during the period for -
Interest paid related to continuing operations	(19,373)	$ (12,828)	$ (7,087)
Income taxes paid	(112,335)	(121,662)	(130,921)
Income tax refunds related to continuing operations	9,845	7,548	23,788
Discontinued Operations
Cash (paid) received during the period for -
Income taxes paid	$ 0	$ (7,260)	$ (144,076)

Quarterly Financial Data (Un119

Quarterly Financial Data (Unaudited) - Consolidated Operating Results by Quarter (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 2,478,627	$ 2,609,307	$ 2,200,374	$ 2,178,170	$ 2,102,966	$ 2,042,186	$ 1,792,430	$ 1,713,737	$ 9,466,478	$ 7,651,319	$ 7,572,436
Gross profit	322,876	350,631	302,165	266,188	307,688	302,582	200,217	203,313	1,241,860	1,013,800	923,665
Net income	115,576	89,849	64,360	48,440	88,358	74,152	16,729	20,859	318,225	200,098	321,824
Net income attributable to common stock	113,561	89,313	63,837	48,267	87,583	73,742	16,562	20,496	314,978	198,383	310,907
Net income from continuing operations attributable to common stock	$ 113,561	$ 89,313	$ 63,837	$ 48,267	$ 88,530	$ 73,137	$ 16,562	$ 20,496	$ 314,978	$ 198,725	$ 120,286
Basic earnings per share from continuing operations attributable to common stock (in usd per share)	$ 0.72	$ 0.57	$ 0.41	$ 0.31	$ 0.57	$ 0.47	$ 0.11	$ 0.13	$ 2.02	$ 1.26	$ 0.62
Diluted earnings per share from continuing operations attributable to common stock (in usd per share)	$ 0.72	$ 0.56	$ 0.41	$ 0.31	$ 0.57	$ 0.47	$ 0.11	$ 0.13	$ 2	$ 1.26	$ 0.62

Quarterly Financial Data (Un120

Quarterly Financial Data (Unaudited) - Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Asset impairment charges	$ 58,100		$ 58,057	$ 7,964	$ 58,451
Asset impairment charges, net of tax	$ 36,600	$ 7,100
Impairment of long-lived assets to be disposed of		$ 8,000		$ 8,000

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ in Millions	1 Months Ended
	Jan. 31, 2018	Dec. 31, 2017
Subsequent Event [Line Items]
Contingent consideration, maximum		$ 139.5
Electrical Infrastructure Services Business and Postsecondary Educational Institution | Subsequent Event
Subsequent Event [Line Items]
Aggregate consideration paid	$ 47.9
Number of shares granted for acquired companies (in shares)	379,817
Value of Quanta common stock issued	$ 13.6
Contingent consideration, maximum	$ 15