Significant Accounting Policies	3 Months Ended
Mar. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Our significant accounting policies are detailed in "Note 1. Description of Company and Significant Accounting Policies" of our Annual Report on Form 10-K for the year ended December 31, 2017. The following section includes revised accounting policies related to the adoption of ASC Topic 606 and the separate presentation of acquisition and integration related costs. Revenue Recognition Revenue is measured based on the amount of consideration specified in a contract with a customer. Revenue is recognized when and as our performance obligations under the terms of the contract are satisfied which generally occurs with the transfer of control of the goods or services to the customer. To determine the proper revenue recognition method for contracts, we evaluate whether two or more contracts should be combined and accounted for as one single contract and whether the combined or single contract should be accounted for as more than one performance obligation. This evaluation requires significant judgment and the decision to combine a group of contracts or separate a combined or single contract into multiple performance obligations could change the amount of revenue and profit recorded in a given period. Contracts are considered to have a single performance obligation if the promise to transfer the individual goods or services is not separately identifiable from other promises in the contracts, which is mainly because we provide a significant service of integrating a complex set of tasks and components into a single project or capability. Contracts that cover multiple phases of the product lifecycle (development, construction and maintenance & support) are typically considered to have multiple performance obligations even when they are part of a single contract. For contracts with multiple performance obligations, we allocate the transaction price to each performance obligation using our best estimate of the standalone selling price of each distinct good or service in the contract. In cases where we do not provide the distinct good or service on a standalone basis, the primary method used to estimate standalone selling price is the expected cost plus a margin approach, under which we forecast our expected costs of satisfying a performance obligation and then add an appropriate margin for that distinct good or service. We provide product warranties to customers that are included in the sale and are not priced or sold separately or do not provide customers with a service in addition to assurance of compliance with agreed-upon specifications. We do not consider these types of warranties to be separate performance obligations. The following is a description of the principal activities from which we generate revenues by reportable segment: Government Services For most of government services, the customer contracts with us to provide support solutions to defense, space, aviation and other programs and missions through long-term service contracts. The performance obligations related to these long-term service contracts are primarily created through the issuance of task orders by the customer because a service contract generally does not meet the criteria to be considered a contract under ASC 606 since it does not obligate the customer to issue any task orders and could be canceled without substantive penalty under termination for convenience clauses. Accordingly, each task order releases us to perform specific portions of the overall scope in the service contract and is typically accounted for as a separate contract because the task order establishes the enforceable rights and obligations, and payment terms. Task orders can include option periods that may be approved by the customer at a later date depending on the customer's future needs and budget availability. Many of our government services contracts include variable consideration consisting of base fees (a profit percentage applied to our cost) or award fees (additional consideration based on performance criteria, subject to final customer approval). Variable consideration can also arise from modifications to the scope of services resulting in unapproved change orders or customer claims. Variable consideration is included in the transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Our estimates of variable consideration and determination of whether to include estimated amounts in the transaction price are based largely on assessments of legal enforceability, our performance, and all information (historical, current, and forecasted) that is reasonably available to us. Many of our government services contracts are for labor at agreed per hour rates on a cost reimbursable basis to the customer. These contracts are accounted for as a series of distinct services because the labor is provided as a continuous service, each time increment of labor provided is distinct, the nature of the services provided is substantially the same, and the pattern of transfer is the same. In this type of contract, the entire amount of consideration is recognized as labor is provided. We also enter into base operations support contracts to provide the resources to operate bases, installations, camps, and stations of military departments. Our base operations support contracts are either fixed price contracts or cost reimbursable contracts. For fixed price contracts, we recognize a fixed monthly fee as revenue as services are provided because the base operations represent a series of distinct services and our level of effort remains substantially the same from month to month. For cost reimbursable contracts, we bill the customer all direct costs incurred each month plus an agreed provisional rate for overhead and fee. Overhead and fee are finalized at a later date. For the purpose of revenue recognition of the variable elements of the contracts, we apply the variable consideration considerations described above. Revenue on our other types of government services contracts is primarily recognized over time using the cost-to-cost input measure (e.g., costs incurred to date relative to total estimated costs at completion) to measure progress because it best depicts the transfer of assets to the customer which occurs as we incur costs on the contracts. Contract costs include actual direct project costs incurred and an allocation of our indirect costs. Under the typical payment terms of our government services contracts, amounts are billed as work progresses in accordance with agreed-upon contractual terms, either at periodic intervals (e.g., biweekly or monthly) or upon achievement of contractual milestones. Hydrocarbons Services For most of our hydrocarbons services projects, the customer contracts with us to provide a significant service of integrating a complex set of tasks and components into a single project or capability and are therefore accounted for as single performance obligations. It is common for our hydrocarbons services contracts to contain incentive fees, performance bonuses, penalties (liquidated damages) or other provisions, including claims and change orders, that may either increase or decrease the transaction price. Incentives and other performance bonuses generally are awarded upon achievement of certain performance metrics, program milestones or cost targets. Liquidated damage penalties in our contracts are generally capped at a percentage of the contract value. Liquidated damages may be related to schedule delays, typically calculated based on a daily rate, or tied to performance guarantees. Substantially all of our performance obligations related to hydrocarbons services contracts are satisfied over time as work progresses. Typically, revenue is recognized over time using the cost-to-cost input measure to measure progress because it best depicts the transfer of goods and services to the customer which occurs as we incur costs on our contracts. Contract costs include all direct material and labor costs and those indirect costs related to contract performance. Indirect costs, included in cost of revenues, include charges for such items as facilities, engineering, project management, quality control, bids and proposals and procurement. Under the typical payment terms of our hydrocarbons services contracts, the customer makes advance payments as well as interim payments as work progresses. The advance payment generally is not considered a significant financing component as we normally expect to recognize the advance payments in revenue within a year of receipt as work progresses on the related performance obligation. Technology Our technology contracts consist primarily of licensing, basic engineering design (together, the "LBED"), proprietary equipment ("PEQ") or catalyst contracts. LBED contracts are combined into one performance obligation as they are entered into at the same time and the licensed technology requires engineering and design. We may further combine LBED and PEQ contracts into one performance obligation if the contracts were negotiated as a package with a single commercial objective, and the customer contracts with us to provide a significant service of integrating these distinct goods and services into a single project or capability. It is common for our technology contracts to contain variable consideration including contingent milestone payments and penalties (liquidated damages) that may increase or decrease the transaction price. Contingent milestone payments are primarily related to decisions made by the customer after LBED has been completed, such as go or no-go decision on the project. Liquidated damage penalties in our technology contracts are typically calculated based on a weekly rate and are capped at a percentage of the contract value. Substantially all of our performance obligations related to technology contracts are satisfied over time as work progresses. Typically, revenue is recognized over time using the cost-to-cost input measure to measure progress because it best depicts the transfer of assets to the customer which occurs as we incur costs on our contracts. Contract costs include all direct material and labor costs and those indirect costs related to contract performance and are recognized as the performance obligation is satisfied. Under the typical payment terms of our technology contracts, the customer makes advance payments as well as interim payments as work progresses and certain progress milestones are met. The advance payment generally is not considered a significant financing component as we normally expect to recognize the advance payments in revenue within a year of receipt as work progresses on the related performance obligation. Contract Estimates Contract Modifications Due to the nature of the work required to be performed on many of our performance obligations, the estimation of total revenue and cost at completion is complex, subject to many variables and requires significant judgment. As a significant change in one or more of these estimates could affect the profitability of our contracts, we review and update our contract-related estimates regularly through a Company-wide disciplined project review process in which management reviews the progress and execution of our performance obligations and the estimate at completion (EAC). As part of this process, management reviews information including, but not limited to, any outstanding key contract matters, progress towards completion and the related program schedule and the related changes in estimates of revenues and costs. Management must make assumptions and estimates regarding labor productivity and availability, the complexity of the work to be performed, the cost and availability of materials, the performance of subcontractors, and the availability and timing of funding from the customer, among other variables. We recognize adjustments in estimated profit on contracts under the cumulative catch-up method. Under this method, the impact of the adjustment on profit recorded to date is recognized in the period the adjustment is identified. Revenue and profit in future periods of contract performance is recognized using the adjusted estimate. If at any time the estimate of contract profitability indicates an anticipated loss on the contract, we recognize the total loss in the period it is identified. Contracts are often modified to account for changes in contract specifications and requirements. We consider contract modifications to exist when the modification either creates new or changes the existing enforceable rights and obligations. Most of our contract modifications are for goods or services that are not distinct from existing contracts due to the significant integration provided in the context of the contract and are accounted for as if they were part of the original contract. The effect of a contract modification on the transaction price and our measure of progress for the performance obligation to which it relates, is recognized as an adjustment to revenue (either as an increase in or a reduction of revenue) on a cumulative catch-up basis. We account for contract modifications as a separate contract when the modification results in the promise to deliver additional goods or services that are distinct and the increase in price of the contract is for the same amount as the stand-alone selling price of the additional goods or services included in the modification. We estimate variable consideration at the most likely amount to which we expect to be entitled. Any variable consideration is included in the transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Our estimates of variable consideration and determination of whether to include estimated amounts in the transaction price are based largely on assessments of legal enforceability, our performance, and all information (historical, current, and forecasted) that is reasonably available to us. We allocate variable consideration entirely to a performance obligation or to a distinct good or service within a performance obligation if it relates specifically to our efforts to satisfy the performance obligation or transfer the distinct good or service, and the allocation depicts the amount of consideration to which we expect to be entitled. Claims Against Vendors and Subcontractors We include claims to vendors, subcontractors and others as a receivable and a reduction in recognized costs when enforceability of the claim is established by the contract and the amounts are reasonably estimable and probable of being recovered. The amounts are recorded up to the extent of the lesser of the amounts management expects to recover or to costs incurred. Our net revenue recognized from performance obligations satisfied in previous periods was immaterial to our financial statements for the three month period ended March 31, 2018. On March 31, 2018, we had $9.9 billion of transaction price allocated to remaining performance obligations. We expect to recognize approximately 25% of our remaining performance obligations as revenue within one year and the balance thereafter. Revenue associated with our remaining performance obligations to be recognized beyond one year includes performance obligations related to Aspire Defence and Fasttrax projects, which have contract terms extending through 2041 and 2023, respectively. The balance of remaining performance obligations does not include variable consideration that was determined to be constrained as of March 31, 2018. Accounts receivable Accounts receivable are recorded based on contracted prices when we obtain an unconditional right to payment under the terms of our contracts. We establish an allowance for doubtful accounts based on the assessment of our clients' willingness and ability to pay. In addition to such allowances, there are often items in dispute or being negotiated that may require us to make an estimate as to the ultimate outcome. Past due receivable balances are written off when our internal collection efforts have been unsuccessful in collecting the amounts due. Contract assets and liabilities Billing practices are governed by the contract terms of each project based upon costs incurred, achievement of milestones or pre-agreed schedules. Billings do not necessarily correlate with revenue recognized using the cost-to-cost method of revenue recognition. Contract assets include unbilled amounts typically resulting from revenue under long-term contracts when the cost-to-cost method of revenue recognition is utilized and revenue recognized exceeds the amount billed to the customer, and right to payment is not unconditional. Contract liabilities consist of advance payments and billings in excess of revenue recognized and deferred revenue. Retainage, included in contract assets, represents the amounts withheld from billings by our clients pursuant to provisions in the contracts and may not be paid to us until the completion of specific tasks or the completion of the project and, in some instances, for even longer periods. Retainage may also be subject to restrictive conditions such as performance guarantees. Our retainage excludes amounts withheld by the U.S. government on certain contracts. See Notes 10 and 16 to our condensed consolidated financial statements for our discussion on U.S. government receivables. Our contract assets and liabilities are reported in a net position on a contract-by-contract basis at the end of each reporting period. We classify advance payments and billings in excess of revenue recognized as current and deferred revenue as current or noncurrent based on the timing of when we expect to recognize revenue. The noncurrent portion of deferred revenue is included in "Other liabilities" in our condensed consolidated balance sheets. Acquisition and integration related costs Acquisition and integration related costs consist of third party transaction expenses representing legal, consulting and investment banking-related costs that are direct, incremental costs incurred prior to the closing of an acquisition and costs incurred to integrate the operations of newly acquired businesses into the Company's existing infrastructure as well as other initiatives to combine the newly merged companies into new infrastructure.

Our significant accounting policies are detailed in "Note 1. Description of Company and Significant Accounting Policies" of our Annual Report on Form 10-K for the year ended December 31, 2017. The following section includes revised accounting policies related to the adoption of ASC Topic 606 and the separate presentation of acquisition and integration related costs.

Revenue is measured based on the amount of consideration specified in a contract with a customer. Revenue is recognized when and as our performance obligations under the terms of the contract are satisfied which generally occurs with the transfer of control of the goods or services to the customer.

To determine the proper revenue recognition method for contracts, we evaluate whether two or more contracts should be combined and accounted for as one single contract and whether the combined or single contract should be accounted for as more than one performance obligation. This evaluation requires significant judgment and the decision to combine a group of contracts or separate a combined or single contract into multiple performance obligations could change the amount of revenue and profit recorded in a given period. Contracts are considered to have a single performance obligation if the promise to transfer the individual goods or services is not separately identifiable from other promises in the contracts, which is mainly because we provide a significant service of integrating a complex set of tasks and components into a single project or capability. Contracts that cover multiple phases of the product lifecycle (development, construction and maintenance & support) are typically considered to have multiple performance obligations even when they are part of a single contract.

For contracts with multiple performance obligations, we allocate the transaction price to each performance obligation using our best estimate of the standalone selling price of each distinct good or service in the contract. In cases where we do not provide the distinct good or service on a standalone basis, the primary method used to estimate standalone selling price is the expected

We provide product warranties to customers that are included in the sale and are not priced or sold separately or do not provide customers with a service in addition to assurance of compliance with agreed-upon specifications. We do not consider these types of warranties to be separate performance obligations.

For most of government services, the customer contracts with us to provide support solutions to defense, space, aviation and other programs and missions through long-term service contracts. The performance obligations related to these long-term service contracts are primarily created through the issuance of task orders by the customer because a service contract generally does not meet the criteria to be considered a contract under ASC 606 since it does not obligate the customer to issue any task orders and could be canceled without substantive penalty under termination for convenience clauses. Accordingly, each task order releases us to perform specific portions of the overall scope in the service contract and is typically accounted for as a separate contract because the task order establishes the enforceable rights and obligations, and payment terms. Task orders can include option periods that may be approved by the customer at a later date depending on the customer's future needs and budget availability.

Many of our government services contracts include variable consideration consisting of base fees (a profit percentage applied to our cost) or award fees (additional consideration based on performance criteria, subject to final customer approval). Variable consideration can also arise from modifications to the scope of services resulting in unapproved change orders or customer claims. Variable consideration is included in the transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Our estimates of variable consideration and determination of whether to include estimated amounts in the transaction price are based largely on assessments of legal enforceability, our performance, and all information (historical, current, and forecasted) that is reasonably available to us.

Many of our government services contracts are for labor at agreed per hour rates on a cost reimbursable basis to the customer. These contracts are accounted for as a series of distinct services because the labor is provided as a continuous service, each time increment of labor provided is distinct, the nature of the services provided is substantially the same, and the pattern of transfer is the same. In this type of contract, the entire amount of consideration is recognized as labor is provided.

We also enter into base operations support contracts to provide the resources to operate bases, installations, camps, and stations of military departments. Our base operations support contracts are either fixed price contracts or cost reimbursable contracts. For fixed price contracts, we recognize a fixed monthly fee as revenue as services are provided because the base operations represent a series of distinct services and our level of effort remains substantially the same from month to month. For cost reimbursable contracts, we bill the customer all direct costs incurred each month plus an agreed provisional rate for overhead and fee. Overhead and fee are finalized at a later date. For the purpose of revenue recognition of the variable elements of the contracts, we apply the variable consideration considerations described above.

Revenue on our other types of government services contracts is primarily recognized over time using the cost-to-cost input measure (e.g., costs incurred to date relative to total estimated costs at completion) to measure progress because it best depicts the transfer of assets to the customer which occurs as we incur costs on the contracts. Contract costs include actual direct project costs incurred and an allocation of our indirect costs.

Under the typical payment terms of our government services contracts, amounts are billed as work progresses in accordance with agreed-upon contractual terms, either at periodic intervals (e.g., biweekly or monthly) or upon achievement of contractual milestones.

For most of our hydrocarbons services projects, the customer contracts with us to provide a significant service of integrating a complex set of tasks and components into a single project or capability and are therefore accounted for as single performance obligations.

It is common for our hydrocarbons services contracts to contain incentive fees, performance bonuses, penalties (liquidated damages) or other provisions, including claims and change orders, that may either increase or decrease the transaction price.

Incentives and other performance bonuses generally are awarded upon achievement of certain performance metrics, program milestones or cost targets. Liquidated damage penalties in our contracts are generally capped at a percentage of the contract value. Liquidated damages may be related to schedule delays, typically calculated based on a daily rate, or tied to performance guarantees.

Substantially all of our performance obligations related to hydrocarbons services contracts are satisfied over time as work progresses. Typically, revenue is recognized over time using the cost-to-cost input measure to measure progress because it best depicts the transfer of goods and services to the customer which occurs as we incur costs on our contracts. Contract costs include all direct material and labor costs and those indirect costs related to contract performance. Indirect costs, included in cost of revenues, include charges for such items as facilities, engineering, project management, quality control, bids and proposals and procurement.

Under the typical payment terms of our hydrocarbons services contracts, the customer makes advance payments as well as interim payments as work progresses. The advance payment generally is not considered a significant financing component as we normally expect to recognize the advance payments in revenue within a year of receipt as work progresses on the related performance obligation.

Our technology contracts consist primarily of licensing, basic engineering design (together, the "LBED"), proprietary equipment ("PEQ") or catalyst contracts. LBED contracts are combined into one performance obligation as they are entered into at the same time and the licensed technology requires engineering and design. We may further combine LBED and PEQ contracts into one performance obligation if the contracts were negotiated as a package with a single commercial objective, and the customer contracts with us to provide a significant service of integrating these distinct goods and services into a single project or capability.

It is common for our technology contracts to contain variable consideration including contingent milestone payments and penalties (liquidated damages) that may increase or decrease the transaction price. Contingent milestone payments are primarily related to decisions made by the customer after LBED has been completed, such as go or no-go decision on the project. Liquidated damage penalties in our technology contracts are typically calculated based on a weekly rate and are capped at a percentage of the contract value.

Substantially all of our performance obligations related to technology contracts are satisfied over time as work progresses. Typically, revenue is recognized over time using the cost-to-cost input measure to measure progress because it best depicts the transfer of assets to the customer which occurs as we incur costs on our contracts. Contract costs include all direct material and labor costs and those indirect costs related to contract performance and are recognized as the performance obligation is satisfied.

Under the typical payment terms of our technology contracts, the customer makes advance payments as well as interim payments as work progresses and certain progress milestones are met. The advance payment generally is not considered a significant financing component as we normally expect to recognize the advance payments in revenue within a year of receipt as work progresses on the related performance obligation.

Due to the nature of the work required to be performed on many of our performance obligations, the estimation of total revenue and cost at completion is complex, subject to many variables and requires significant judgment.

As a significant change in one or more of these estimates could affect the profitability of our contracts, we review and update our contract-related estimates regularly through a Company-wide disciplined project review process in which management reviews the progress and execution of our performance obligations and the estimate at completion (EAC). As part of this process, management reviews information including, but not limited to, any outstanding key contract matters, progress towards completion and the related program schedule and the related changes in estimates of revenues and costs. Management must make assumptions and estimates regarding labor productivity and availability, the complexity of the work to be performed, the cost and availability of materials, the performance of subcontractors, and the availability and timing of funding from the customer, among other variables.

We recognize adjustments in estimated profit on contracts under the cumulative catch-up method. Under this method, the impact of the adjustment on profit recorded to date is recognized in the period the adjustment is identified. Revenue and profit in future periods of contract performance is recognized using the adjusted estimate. If at any time the estimate of contract profitability indicates an anticipated loss on the contract, we recognize the total loss in the period it is identified.

Contracts are often modified to account for changes in contract specifications and requirements. We consider contract modifications to exist when the modification either creates new or changes the existing enforceable rights and obligations. Most of our contract modifications are for goods or services that are not distinct from existing contracts due to the significant integration provided in the context of the contract and are accounted for as if they were part of the original contract. The effect of a contract modification on the transaction price and our measure of progress for the performance obligation to which it relates, is recognized as an adjustment to revenue (either as an increase in or a reduction of revenue) on a cumulative catch-up basis.

We account for contract modifications as a separate contract when the modification results in the promise to deliver additional goods or services that are distinct and the increase in price of the contract is for the same amount as the stand-alone selling price of the additional goods or services included in the modification.

We estimate variable consideration at the most likely amount to which we expect to be entitled. Any variable consideration is included in the transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Our estimates of variable consideration and determination of whether to include estimated amounts in the transaction price are based largely on assessments of legal enforceability, our performance, and all information (historical, current, and forecasted) that is reasonably available to us.

We allocate variable consideration entirely to a performance obligation or to a distinct good or service within a performance obligation if it relates specifically to our efforts to satisfy the performance obligation or transfer the distinct good or service, and the allocation depicts the amount of consideration to which we expect to be entitled.

We include claims to vendors, subcontractors and others as a receivable and a reduction in recognized costs when enforceability of the claim is established by the contract and the amounts are reasonably estimable and probable of being recovered. The amounts are recorded up to the extent of the lesser of the amounts management expects to recover or to costs incurred.

On March 31, 2018, we had $9.9 billion of transaction price allocated to remaining performance obligations. We expect to recognize approximately 25% of our remaining performance obligations as revenue within one year and the balance thereafter. Revenue associated with our remaining performance obligations to be recognized beyond one year includes performance obligations related to Aspire Defence and Fasttrax projects, which have contract terms extending through 2041 and 2023, respectively. The balance of remaining performance obligations does not include variable consideration that was determined to be constrained as of March 31, 2018.

We establish an allowance for doubtful accounts based on the assessment of our clients' willingness and ability to pay. In addition to such allowances, there are often items in dispute or being negotiated that may require us to make an estimate as to the ultimate outcome. Past due receivable balances are written off when our internal collection efforts have been unsuccessful in collecting the amounts due.

Billing practices are governed by the contract terms of each project based upon costs incurred, achievement of milestones or pre-agreed schedules. Billings do not necessarily correlate with revenue recognized using the cost-to-cost method of revenue recognition. Contract assets include unbilled amounts typically resulting from revenue under long-term contracts when the cost-to-cost method of revenue recognition is utilized and revenue recognized exceeds the amount billed to the customer, and right to payment is not unconditional. Contract liabilities consist of advance payments and billings in excess of revenue recognized and deferred revenue.

Retainage, included in contract assets, represents the amounts withheld from billings by our clients pursuant to provisions in the contracts and may not be paid to us until the completion of specific tasks or the completion of the project and, in some

instances, for even longer periods. Retainage may also be subject to restrictive conditions such as performance guarantees. Our retainage excludes amounts withheld by the U.S. government on certain contracts. See Notes 10 and 16 to our condensed consolidated financial statements for our discussion on U.S. government receivables.

Our contract assets and liabilities are reported in a net position on a contract-by-contract basis at the end of each reporting period. We classify advance payments and billings in excess of revenue recognized as current and deferred revenue as current or noncurrent based on the timing of when we expect to recognize revenue. The noncurrent portion of deferred revenue is included in "Other liabilities" in our condensed consolidated balance sheets.