New Accounting Pronouncements	12 Months Ended
New Accounting Pronouncements	Dec. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Pronouncements	NEW ACCOUNTING PRONOUNCEMENTS: Adoption of New Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued an update that superseded most revenue recognition guidance, as well as certain cost recognition guidance.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 additional 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, and information about contract balances and performance obligations. Quanta adopted the new revenue recognition guidance using the modified retrospective transition method effective January 1, 2018, applying the guidance to contracts that were not substantially complete as of such date. Quanta’s financial results for reporting periods after January 1, 2018 have been and 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. The net cumulative adjustment resulting from adoption was a $1.3 million reduction to retained earnings as of January 1, 2018, which represented a $1.8 million decrease to revenue recognized prior to adoption, net of $0.5 million in taxes. This adjustment primarily related to certain contracts that are now accounted for as a single performance obligation but were previously accounted for separately for revenue recognition purposes. Quanta has not experienced significant changes to the pattern of revenue recognition for its contracts, the identification of contracts and performance obligations or the measurement of variable consideration. For the year ended December 31, 2018, the impact related to the adoption of the new revenue recognition guidance on revenues, contract assets and contract liabilities was immaterial. If Quanta had not adopted the new revenue recognition guidance effective January 1, 2018, it would have recognized $2.0 million of additional revenues during the year ended December 31, 2018. Quanta has also expanded its discussion in Note 2 above to address the quantitative and qualitative disclosure requirements of the new revenue recognition standard. 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 observable price changes in orderly transactions for an identical or a similar investment of the same company. Quanta adopted 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 continues to measure these investments at cost less any impairments and also considers 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 number and amount of equity investments held at the time of adoption. 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 requires application using a retrospective transition method. Quanta adopted this guidance effective January 1, 2018, and the changes did not have a material impact on its consolidated financial statements. In October 2016, the FASB issued an update that requires 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 should be recognized at the time of the transfer. The new guidance does 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. Quanta adopted this guidance effective January 1, 2018 utilizing the modified retrospective method, and the changes did not 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. Additionally, restricted cash balances for each period are 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 is no longer reported on Quanta’s consolidated statements of cash flows. Quanta adopted this guidance effective January 1, 2018 utilizing the retrospective transition method, and the changes did not have a material impact on its consolidated financial statements. See Note 15 for reconciliations of “Cash and cash equivalents” and restricted cash. In January 2017, the FASB issued an update intended to clarify whether transactions should be accounted for as acquisitions or disposals of assets or businesses. 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 requires, 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. Quanta adopted this guidance effective January 1, 2018 utilizing the prospective transition method, and the changes did not materially impact its consolidated financial statements. 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. Quanta adopted this guidance effective January 1, 2018 using the prospective transition method, and the changes did not materially impact its consolidated financial statements. In June 2018, the FASB issued an update that expands the scope of share-based payment accounting to include share-based payment transactions for acquiring goods and services from non-employees. Quanta adopted this guidance in 2018, which did not materially impact Quanta’s consolidated financial statements. In August 2018, the FASB issued an update that aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). Quanta adopted this guidance in 2018, which did not materially impact Quanta’s consolidated financial statements. Quanta will apply the new guidance prospectively. Accounting Standards Not Yet Adopted In February 2016, the FASB issued an update that requires the recognition of operating lease right-of-use assets and the corresponding lease liabilities on the balance sheet. The new standard is effective for interim and annual periods beginning after December 15, 2018. In July 2018, the FASB issued an update that provides entities a choice between the previously required modified retrospective transition method and another transition method that allows entities to initially apply the new standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. Quanta established a cross-functional team to implement this standard and evaluated arrangements that would be subject to the standard, implemented software to meet the reporting and disclosure requirements of the standard and assessed the impact of the standard on its processes and internal controls. Quanta plans to elect the practical expedients that permit it to retain the identification and classification of leases under the previous accounting guidance, as well as an expedient where leases with terms of twelve months or less are not recorded on the balance sheet. Quanta will adopt this guidance effective January 1, 2019. Quanta anticipates recording lease right-of-use assets and lease liabilities in similar amounts of between approximately $280 million and $320 million on its consolidated balance sheet as of January 1, 2019, with any difference between the right-of-use assets and lease liabilities being recorded as a cumulative effect adjustment as of such date. The update is not anticipated to have a material effect on Quanta’s consolidated statement of operations and is not expected to have a material impact on Quanta’s compliance with the financial covenants under its senior secured credit facility. 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 effective January 1, 2020. In August 2017, the FASB issued an update that 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 effective January 1, 2019; however, as of December 31, 2018, Quanta had no hedging relationships outstanding. In August 2018, the FASB issued an update that amends certain disclosure requirements related to fair value measurements. Certain disclosure requirements will be removed, such as the valuation processes for Level 3 fair value measurements, and other disclosure requirements will be modified or added, including a new requirement to disclose the range and weighted average (or a more reasonable and rational method to reflect the distribution) of significant unobservable inputs used to develop Level 3 fair value measurements. This update is effective for interim and annual periods beginning after December 15, 2019. Certain amendments, including the disclosure of the range and weighted average of significant observable inputs used to develop Level 3 fair value measurements, should be applied prospectively, while other amendments should be applied retrospectively. Quanta is evaluating the impact of this new standard on its consolidated financial statements and will adopt the new standard effective January 1, 2020.