Basis of Presentation and Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	We have presented the condensed consolidated financial statements of BWX Technologies, Inc. ("BWXT" or the "Company") in U.S. dollars in accordance with the interim reporting requirements of Form 10-Q, Rule 10-01 of Regulation S-X and accounting principles generally accepted in the United States ("GAAP"). Certain financial information and disclosures normally included in our financial statements prepared annually in accordance with GAAP have been condensed or omitted. Readers of these financial statements should, therefore, refer to the consolidated financial statements and notes in our annual report on Form 10-K for the year ended December 31, 2019 (our "2019 10-K"). We have included all adjustments, in the opinion of management, consisting only of normal recurring adjustments, necessary for a fair presentation.
Consolidation	We use the equity method to account for investments in entities that we do not control, but over which we have the ability to exercise significant influence. We generally refer to these entities as "joint ventures." We have eliminated all intercompany transactions and accounts. We have reclassified certain amounts previously reported to conform to the presentation at June 30, 2020 and for the three and six months ended June 30, 2020. We present the notes to our condensed consolidated financial statements on the basis of continuing operations, unless otherwise stated. Unless the context otherwise indicates, "we," "us" and "our" mean BWXT and its consolidated subsidiaries.
Reclassification	We have reclassified certain amounts previously reported to conform to the presentation at June 30, 2020 and for the three and six months ended June 30, 2020.
Reportable Segments	Reportable Segments We operate in three reportable segments: Nuclear Operations Group, Nuclear Power Group and Nuclear Services Group. Our reportable segments are further described as follows: •Our Nuclear Operations Group segment manufactures naval nuclear reactors for the U.S. Naval Nuclear Propulsion Program for use in submarines and aircraft carriers. Through this segment, we own and operate manufacturing facilities located in Lynchburg, Virginia; Barberton, Ohio; Mount Vernon, Indiana; Euclid, Ohio; and Erwin, Tennessee. The Lynchburg operations fabricate fuel-bearing precision components that range in weight from a few grams to hundreds of tons. In-house capabilities also include wet chemistry uranium processing, advanced heat treatment to optimize component material properties and a controlled, clean-room environment with the capacity to assemble railcar-size components. The Barberton and Mount Vernon locations specialize in the design and manufacture of heavy components inclusive of development and fabrication activities for submarine missile launch tubes. The Euclid facility fabricates electro-mechanical equipment and performs design, manufacturing, inspection, assembly and testing activities. Fuel for the naval nuclear reactors is provided by Nuclear Fuel Services, Inc. ("NFS"), one of our wholly owned subsidiaries. Located in Erwin, NFS also downblends Cold War-era government stockpiles of high-enriched uranium into material suitable for further processing into commercial nuclear reactor fuel. •Our Nuclear Power Group segment fabricates commercial nuclear steam generators, nuclear fuel, fuel handling systems, pressure vessels, reactor components, heat exchangers, tooling delivery systems and other auxiliary equipment, including containers for the storage of spent nuclear fuel and other high-level waste and supplies nuclear-grade materials and precisely machined components for nuclear utility customers. BWXT has supplied the nuclear industry with more than 1,300 large, heavy components worldwide and is the only commercial heavy nuclear component manufacturer in North America. This segment also provides specialized engineering services that include structural component design, 3-D thermal-hydraulic engineering analysis, weld and robotic process development, electrical and controls engineering and metallurgy and materials engineering. In addition, this segment offers in-plant inspection, maintenance and modification services for nuclear steam generators, heat exchangers, reactors, fuel handling systems and balance of plant equipment, as well as specialized non-destructive examination and tooling/repair solutions. This segment is also a leading global manufacturer and supplier of critical medical radioisotopes and radiopharmaceuticals for research, diagnostic and therapeutic uses. •Our Nuclear Services Group segment provides various services to the U.S. Government and the commercial nuclear industry. Services provided to the U.S. Government include nuclear materials management and operation, environmental management and administrative and operating services for various U.S. Government-owned facilities. These services are provided to the U.S. Department of Energy ("DOE"), including the National Nuclear Security Administration ("NNSA"), the Office of Nuclear Energy, the Office of Science and the Office of Environmental Management, and NASA. Through this segment we deliver services and management solutions to nuclear and high- consequence operations. A significant portion of this segment's operations are conducted through joint ventures. This segment also develops technology for a variety of applications, including advanced nuclear power sources, and offers complete advanced nuclear fuel and reactor design and engineering, licensing and manufacturing services for new advanced nuclear reactors.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards On January 1, 2020, we adopted the update to the Financial Accounting Standards Board ("FASB") Topic Financial Instruments – Credit Losses. This update requires entities to recognize expected credit losses immediately in the financial statements. We considered our customer base, credit loss history and expected loss rate in our evaluation of expected credit losses. The adoption of the provisions in this update did not have an impact on our financial position, results of operations or cash flows. On January 1, 2020, we adopted the update to the FASB Topic Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. This update simplifies the accounting for goodwill impairment by eliminating the second step from the goodwill impairment test. Goodwill impairment will now be determined by comparing the fair value of a reporting unit with its carrying amount. The adoption of the provisions in this update did not have an impact on our financial position, results of operations or cash flows.
Contracts and Revenue Recognition	Contracts and Revenue Recognition We generally recognize contract revenues and related costs over time for individual performance obligations based on a cost-to-cost method in accordance with FASB Topic Revenue from Contracts with Customers. We recognize estimated contract revenue and resulting income based on the measurement of the extent of progress toward completion as a percentage of the total project. Certain costs may be excluded from the cost-to-cost method of measuring progress, such as significant costs for uninstalled materials, if such costs do not depict our performance in transferring control of goods or services to the customer. We review contract price and cost estimates periodically as the work progresses and reflect adjustments proportionate to the percentage-of-completion in income in the period when those estimates are revised. Certain of our contracts recognize revenue at a point in time, and revenue on these contracts is recognized when control transfers to the customer. The majority of our revenue that is recognized at a point in time is related to parts and certain medical radioisotopes and radiopharmaceuticals in our Nuclear Power Group segment. For all contracts, if a current estimate of total contract cost indicates a loss on a contract, the projected loss is recognized in full when determined.
Provision for Income Taxes	Provision for Income Taxes We are subject to federal income tax in the U.S. and Canada as well as income tax within multiple U.S. state jurisdictions. We provide for income taxes based on the enacted tax laws and rates in the jurisdictions in which we conduct our operations. These jurisdictions may have regimes of taxation that vary with respect to nominal rates and with respect to the basis on which these rates are applied. This variation, along with the changes in our mix of income within these jurisdictions, can contribute to shifts in our effective tax rate from period to period.
Cash and Cash Equivalents and Restricted Cash and Cash Equivalents	Cash and Cash Equivalents and Restricted Cash and Cash Equivalents At June 30, 2020, we had restricted cash and cash equivalents totaling $6.0 million, $2.9 million of which was held for future decommissioning of facilities (which is included in Other Assets on our condensed consolidated balance sheets) and $3.1 million of which was held to meet reinsurance reserve requirements of our captive insurer.
Inventories	Inventories At June 30, 2020 and December 31, 2019, Other current assets included inventories totaling $12.0 million and $17.1 million, respectively, consisting entirely of raw materials and supplies.
Derivative Financial Instruments	Derivative Financial Instruments Our operations give rise to exposure to market risks from changes in foreign currency exchange ("FX") rates. We use derivative financial instruments, primarily FX forward contracts, to reduce the impact of changes in FX rates on our operating results. We use these instruments to hedge our exposure associated with revenues or costs on our long-term contracts and other transactions that are denominated in currencies other than our operating entities' functional currencies. We do not hold or issue derivative financial instruments for trading or other speculative purposes. We enter into derivative financial instruments primarily as hedges of certain firm purchase and sale commitments and loans between domestic and foreign subsidiaries denominated in foreign currencies. We record these contracts at fair value on our condensed consolidated balance sheets. Based on the hedge designation at the inception of the contract, the related gains and losses on these contracts are deferred in stockholders' equity as a component of Accumulated other comprehensive income until the hedged item is recognized in earnings. The gain or loss on a derivative instrument not designated as a hedging instrument is immediately recognized in earnings. Gains and losses on derivative financial instruments that require immediate recognition are included as a component of Other – net on our condensed consolidated statements of income.We have designated the majority of our FX forward contracts that qualify for hedge accounting as cash flow hedges. The hedged risk is the risk of changes in functional-currency-equivalent cash flows attributable to changes in FX spot rates of forecasted transactions primarily related to long-term contracts. We exclude from our assessment of effectiveness the portion of the fair value of the FX forward contracts attributable to the difference between FX spot rates and FX forward rates.

Basis of Presentation and Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2020

We have presented the condensed consolidated financial statements of BWX Technologies, Inc. ("BWXT" or the "Company") in U.S. dollars in accordance with the interim reporting requirements of Form 10-Q, Rule 10-01 of Regulation S-X and accounting principles generally accepted in the United States ("GAAP"). Certain financial information and disclosures normally included in our financial statements prepared annually in accordance with GAAP have been condensed or omitted. Readers of these financial statements should, therefore, refer to the consolidated financial statements and notes in our annual report on Form 10-K for the year ended December 31, 2019 (our "2019 10-K"). We have included all adjustments, in the opinion of management, consisting only of normal recurring adjustments, necessary for a fair presentation.

Consolidation

We use the equity method to account for investments in entities that we do not control, but over which we have the ability to exercise significant influence. We generally refer to these entities as "joint ventures." We have eliminated all intercompany transactions and accounts. We have reclassified certain amounts previously reported to conform to the presentation at June 30, 2020 and for the three and six months ended June 30, 2020. We present the notes to our condensed consolidated financial statements on the basis of continuing operations, unless otherwise stated.

Unless the context otherwise indicates, "we," "us" and "our" mean BWXT and its consolidated subsidiaries.

Reclassification

We have reclassified certain amounts previously reported to conform to the presentation at June 30, 2020 and for the three and six months ended June 30, 2020.

Reportable Segments

We operate in three reportable segments: Nuclear Operations Group, Nuclear Power Group and Nuclear Services Group. Our reportable segments are further described as follows:

•Our Nuclear Operations Group segment manufactures naval nuclear reactors for the U.S. Naval Nuclear Propulsion Program for use in submarines and aircraft carriers. Through this segment, we own and operate manufacturing facilities located in Lynchburg, Virginia; Barberton, Ohio; Mount Vernon, Indiana; Euclid, Ohio; and Erwin, Tennessee. The Lynchburg operations fabricate fuel-bearing precision components that range in weight from a few grams to hundreds of tons. In-house capabilities also include wet chemistry uranium processing, advanced heat treatment to optimize component material properties and a controlled, clean-room environment with the capacity to assemble railcar-size components. The Barberton and Mount Vernon locations specialize in the design and manufacture of heavy components inclusive of development and fabrication activities for submarine missile launch tubes. The Euclid facility fabricates electro-mechanical equipment and performs design, manufacturing, inspection, assembly and testing activities. Fuel for the naval nuclear reactors is provided by Nuclear Fuel Services, Inc. ("NFS"), one of our wholly owned subsidiaries. Located in Erwin, NFS also downblends Cold War-era government stockpiles of high-enriched uranium into material suitable for further processing into commercial nuclear reactor fuel.

•Our Nuclear Power Group segment fabricates commercial nuclear steam generators, nuclear fuel, fuel handling systems, pressure vessels, reactor components, heat exchangers, tooling delivery systems and other auxiliary equipment, including containers for the storage of spent nuclear fuel and other high-level waste and supplies nuclear-grade materials and precisely machined components for nuclear utility customers. BWXT has supplied the nuclear industry with more than 1,300 large, heavy components worldwide and is the only commercial heavy nuclear component manufacturer in North America. This segment also provides specialized engineering services that include structural component design, 3-D thermal-hydraulic engineering analysis, weld and robotic process development, electrical and controls engineering and metallurgy and materials engineering. In addition, this segment offers in-plant inspection, maintenance and modification services for nuclear steam generators, heat exchangers, reactors, fuel handling systems and balance of plant equipment, as well as specialized non-destructive examination and tooling/repair solutions. This segment is also a leading global manufacturer and supplier of critical medical radioisotopes and radiopharmaceuticals for research, diagnostic and therapeutic uses.

•Our Nuclear Services Group segment provides various services to the U.S. Government and the commercial nuclear industry. Services provided to the U.S. Government include nuclear materials management and operation, environmental management and administrative and operating services for various U.S. Government-owned facilities. These services are provided to the U.S. Department of Energy ("DOE"), including the National Nuclear Security Administration ("NNSA"), the Office of Nuclear Energy, the Office of Science and the Office of Environmental Management, and NASA. Through this segment we deliver services and management solutions to nuclear and high-

consequence operations. A significant portion of this segment's operations are conducted through joint ventures. This segment also develops technology for a variety of applications, including advanced nuclear power sources, and offers complete advanced nuclear fuel and reactor design and engineering, licensing and manufacturing services for new advanced nuclear reactors.

Recently Adopted Accounting Standards

On January 1, 2020, we adopted the update to the Financial Accounting Standards Board ("FASB") Topic Financial Instruments – Credit Losses. This update requires entities to recognize expected credit losses immediately in the financial statements. We considered our customer base, credit loss history and expected loss rate in our evaluation of expected credit losses. The adoption of the provisions in this update did not have an impact on our financial position, results of operations or cash flows.

On January 1, 2020, we adopted the update to the FASB Topic Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. This update simplifies the accounting for goodwill impairment by eliminating the second step from the goodwill impairment test. Goodwill impairment will now be determined by comparing the fair value of a reporting unit with its carrying amount. The adoption of the provisions in this update did not have an impact on our financial position, results of operations or cash flows.

Contracts and Revenue Recognition

We generally recognize contract revenues and related costs over time for individual performance obligations based on a cost-to-cost method in accordance with FASB Topic Revenue from Contracts with Customers. We recognize estimated contract revenue and resulting income based on the measurement of the extent of progress toward completion as a percentage of the total project. Certain costs may be excluded from the cost-to-cost method of measuring progress, such as significant costs for uninstalled materials, if such costs do not depict our performance in transferring control of goods or services to the customer. We review contract price and cost estimates periodically as the work progresses and reflect adjustments proportionate to the percentage-of-completion in income in the period when those estimates are revised. Certain of our contracts recognize revenue at a point in time, and revenue on these contracts is recognized when control transfers to the customer. The majority of our revenue that is recognized at a point in time is related to parts and certain medical radioisotopes and radiopharmaceuticals in our Nuclear Power Group segment. For all contracts, if a current estimate of total contract cost indicates a loss on a contract, the projected loss is recognized in full when determined.

Provision for Income Taxes

We are subject to federal income tax in the U.S. and Canada as well as income tax within multiple U.S. state jurisdictions. We provide for income taxes based on the enacted tax laws and rates in the jurisdictions in which we conduct our operations. These jurisdictions may have regimes of taxation that vary with respect to nominal rates and with respect to the basis on which these rates are applied. This variation, along with the changes in our mix of income within these jurisdictions, can contribute to shifts in our effective tax rate from period to period.

Cash and Cash Equivalents and Restricted Cash and Cash Equivalents

At June 30, 2020, we had restricted cash and cash equivalents totaling $6.0 million, $2.9 million of which was held for future decommissioning of facilities (which is included in Other Assets on our condensed consolidated balance sheets) and $3.1 million of which was held to meet reinsurance reserve requirements of our captive insurer.

Inventories

At June 30, 2020 and December 31, 2019, Other current assets included inventories totaling $12.0 million and $17.1 million, respectively, consisting entirely of raw materials and supplies.

Derivative Financial Instruments

Our operations give rise to exposure to market risks from changes in foreign currency exchange ("FX") rates. We use derivative financial instruments, primarily FX forward contracts, to reduce the impact of changes in FX rates on our operating results. We use these instruments to hedge our exposure associated with revenues or costs on our long-term contracts and other transactions that are denominated in currencies other than our operating entities' functional currencies. We do not hold or issue derivative financial instruments for trading or other speculative purposes.

We enter into derivative financial instruments primarily as hedges of certain firm purchase and sale commitments and loans between domestic and foreign subsidiaries denominated in foreign currencies. We record these contracts at fair value on our condensed consolidated balance sheets. Based on the hedge designation at the inception of the contract, the related gains and losses on these contracts are deferred in stockholders' equity as a component of Accumulated other comprehensive income until the hedged item is recognized in earnings. The gain or loss on a derivative instrument not designated as a hedging instrument is immediately recognized in earnings. Gains and losses on derivative financial instruments that require immediate recognition are included as a component of Other – net on our condensed consolidated statements of income.We have designated the majority of our FX forward contracts that qualify for hedge accounting as cash flow hedges. The hedged risk is the risk of changes in functional-currency-equivalent cash flows attributable to changes in FX spot rates of forecasted transactions primarily related to long-term contracts. We exclude from our assessment of effectiveness the portion of the fair value of the FX forward contracts attributable to the difference between FX spot rates and FX forward rates.