BWX (BWXT) 10-Q 6 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Aug. 02, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Trading Symbol	BWXT
Entity Registrant Name	BWX Technologies, Inc.
Entity Central Index Key	1,486,957
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		99,708,611

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents	$ 317,624	$ 203,404
Restricted cash and cash equivalents	5,870	7,105
Investments	1,824	2,934
Accounts receivable – trade, net	200,889	189,217
Accounts receivable – other	14,742	19,365
Contracts in progress	317,405	420,628
Other current assets	32,343	30,437
Total Current Assets	890,697	873,090
Property, Plant and Equipment	1,034,015	1,013,141
Less accumulated depreciation	676,813	664,512
Net Property, Plant and Equipment	357,202	348,629
Investments	8,932	9,301
Goodwill	215,547	218,331
Deferred Income Taxes	84,868	86,740
Investments in Unconsolidated Affiliates	57,854	43,266
Intangible Assets	103,008	110,405
Other Assets	24,357	22,577
TOTAL	1,742,465	1,712,339
Current Liabilities:
Current maturities of long-term debt	14,556	27,870
Accounts payable	88,421	93,421
Accrued employee benefits	67,417	82,477
Accrued liabilities – other	48,377	64,738
Advance billings on contracts	77,775	246,192
Accrued warranty expense	12,822	13,428
Total Current Liabilities	309,368	528,126
Long-Term Debt	666,200	481,059
Accumulated Postretirement Benefit Obligation	20,065	21,368
Environmental Liabilities	80,708	79,786
Pension Liability	259,231	296,444
Other Liabilities	18,576	19,799
Commitments and Contingencies (Note 5)
Stockholders' Equity:
Common stock, par value $0.01 per share, authorized 325,000,000 shares; issued 125,748,071 and 125,381,591 shares at June 30, 2018 and December 31, 2017, respectively	1,257	1,254
Preferred stock, par value $0.01 per share, authorized 75,000,000 shares; No shares issued	0	0
Capital in excess of par value	108,919	98,843
Retained earnings	1,097,665	990,652
Treasury stock at cost, 26,057,475 and 25,964,088 shares at June 30, 2018 and December 31, 2017, respectively	(820,826)	(814,809)
Accumulated other comprehensive income	1,248	9,454
Stockholders' Equity – BWX Technologies, Inc.	388,263	285,394
Noncontrolling interest	54	363
Total Stockholders' Equity	388,317	285,757
TOTAL	$ 1,742,465	$ 1,712,339

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, par value (in usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	325,000,000	325,000,000
Common stock, shares issued (in shares)	125,748,071	125,381,591
Preferred stock, par value (in usd per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	75,000,000	75,000,000
Preferred stock, shares issued (in shares)	0	0
Treasury stock at cost, shares (in shares)	26,057,475	25,964,088

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Revenues	$ 438,921	$ 410,011	$ 896,384	$ 838,240
Costs and Expenses:
Cost of operations	318,209	278,356	645,573	581,572
Research and development costs	4,107	1,152	7,714	2,671
Gains on asset disposals and impairments, net	(237)	(31)	(245)	(31)
Selling, general and administrative expenses	51,518	48,433	105,280	99,530
Total Costs and Expenses	373,597	327,910	758,322	683,742
Equity in Income of Investees	6,225	3,327	13,375	7,202
Operating Income	71,549	85,428	151,437	161,700
Other Income (Expense):
Interest income	441	211	1,219	348
Interest expense	(7,869)	(3,906)	(11,429)	(7,423)
Other – net	15,106	6,749	23,016	14,235
Total Other Income (Expense)	7,678	3,054	12,806	7,160
Income before Provision for Income Taxes	79,227	88,482	164,243	168,860
Provision for Income Taxes	18,493	27,062	37,096	51,654
Net Income	60,734	61,420	127,147	117,206
Net Income Attributable to Noncontrolling Interest	(71)	(157)	(43)	(224)
Net Income Attributable to BWX Technologies, Inc.	$ 60,663	$ 61,263	$ 127,104	$ 116,982
Basic:
Net Income Attributable to BWX Technologies, Inc. (in usd per share)	$ 0.61	$ 0.62	$ 1.28	$ 1.18
Diluted:
Net Income Attributable to BWX Technologies, Inc. (in usd per share)	$ 0.60	$ 0.61	$ 1.26	$ 1.16
Shares used in the computation of earnings per share (Note 10):
Basic (in shares)	99,681,580	99,166,205	99,603,884	99,305,558
Diluted (in shares)	100,571,737	100,150,926	100,542,014	100,420,948

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net Income	$ 60,734	$ 61,420	$ 127,147	$ 117,206
Other Comprehensive Income (Loss):
Currency translation adjustments	(3,609)	2,044	(6,733)	2,835
Derivative financial instruments:
Unrealized (losses) gains arising during the period, net of tax benefit (provision) of $30, $(142), $(29) and $(239), respectively	(127)	409	46	688
Reclassification adjustment for losses (gains) included in net income, net of tax (benefit) provision of $(21), $58, $9 and $71, respectively	64	(170)	(15)	(207)
Amortization of benefit plan costs, net of tax benefit of $(25), $(157), $(208) and $(313), respectively	463	289	785	579
Investments:
Unrealized gains (losses) arising during the period, net of tax provision of $0, $(60), $0 and $(130), respectively	22	(1,210)	(44)	(1,304)
Reclassification adjustment for gains included in net income, net of tax provision of $0, $6, $0 and $14, respectively	0	(120)	0	(134)
Other Comprehensive Income (Loss)	(3,187)	1,242	(5,961)	2,457
Total Comprehensive Income	57,547	62,662	121,186	119,663
Comprehensive Income Attributable to Noncontrolling Interest	(71)	(157)	(43)	(224)
Comprehensive Income Attributable to BWX Technologies, Inc.	$ 57,476	$ 62,505	$ 121,143	$ 119,439

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Tax provision of unrealized gains on derivative financial instruments	$ 30	$ (142)	$ (29)	$ (239)
Tax provision (benefit) on reclassification adjustment for (gains) losses on derivative financial instruments	(21)	58	9	71
Tax benefit of amortization of benefit plan costs	(25)	(157)	(208)	(313)
Tax (provision) benefit of unrealized gains (losses)	0	(60)	0	(130)
Tax provision on reclassification adjustment for gain on investment	$ 0	$ 6	$ 0	$ 14

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Capital In Excess of Par Value	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Stockholders' Equity	Noncontrolling Interest
Beginning balance (in shares) at Dec. 31, 2016		124,149,609
Beginning balance at Dec. 31, 2016	$ 150,410	$ 1,241	$ 22,018	$ 885,117	$ 3,811	$ (762,169)	$ 150,018	$ 392
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	117,206			116,982			116,982	224
Dividends declared	(20,075)			(20,075)			(20,075)
Currency translation adjustments	2,835				2,835		2,835
Derivative financial instruments	481				481		481
Defined benefit obligations	579				579		579
Available-for-sale investments	(1,438)				(1,438)		(1,438)
Exercise of stock options (in shares)		790,922
Exercise of stock options	18,645	$ 8	18,637				18,645
Shares placed in treasury	(11,174)		39,907			(51,081)	(11,174)
Stock-based compensation charges (in shares)		279,776
Stock-based compensation charges	7,098	$ 3	7,095				7,098
Distributions to noncontrolling interests	(266)							(266)
Ending balance (in shares) at Jun. 30, 2017		125,220,307
Ending balance at Jun. 30, 2017	$ 264,301	$ 1,252	87,657	982,024	6,268	(813,250)	263,951	350
Beginning balance (in shares) at Dec. 31, 2017	125,381,591	125,381,591
Beginning balance at Dec. 31, 2017	$ 285,757	$ 1,254	98,843	990,652	9,454	(814,809)	285,394	363
Recently adopted accounting standards at Dec. 31, 2017	9,926			12,171	(2,245)		9,926
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	127,147			127,104			127,104	43
Dividends declared	(32,262)			(32,262)			(32,262)
Currency translation adjustments	(6,733)				(6,733)		(6,733)
Derivative financial instruments	31				31		31
Defined benefit obligations	785				785		785
Available-for-sale investments	(44)				(44)		(44)
Exercise of stock options (in shares)		182,520
Exercise of stock options	4,324	$ 1	4,323				4,324
Shares placed in treasury	(6,017)					(6,017)	(6,017)
Stock-based compensation charges (in shares)		183,960
Stock-based compensation charges	5,755	$ 2	5,753				5,755
Distributions to noncontrolling interests	$ (352)							(352)
Ending balance (in shares) at Jun. 30, 2018	125,748,071	125,748,071
Ending balance at Jun. 30, 2018	$ 388,317	$ 1,257	$ 108,919	$ 1,097,665	$ 1,248	$ (820,826)	$ 388,263	$ 54

Condensed Consolidated Stateme8

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Statement of Stockholders' Equity [Abstract]
Dividends declared per share (in usd per share)	$ 0.32	$ 0.2

Condensed Consolidated Stateme9

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	$ 127,147	$ 117,206
Non-cash items included in net income from continuing operations:
Depreciation and amortization	28,420	28,199
Income of investees, net of dividends	(3,384)	987
Gains on asset disposals and impairments, net	(245)	(31)
Gain on forward contracts	(5,997)	0
Recognition of debt issuance costs from Former Credit Facility	2,441	0
Recognition of losses for pension and postretirement plans	993	892
Stock-based compensation expense	5,755	7,098
Changes in assets and liabilities:
Accounts receivable	(10,858)	(154)
Accounts payable	(3,835)	(26,905)
Contracts in progress and advance billings on contracts	(53,902)	(3,869)
Income taxes	(12,302)	18,477
Accrued and other current liabilities	973	(39,325)
Pension liability, accrued postretirement benefit obligation and employee benefits	(57,439)	(43,790)
Other, net	(457)	5,320
NET CASH PROVIDED BY OPERATING ACTIVITIES	17,310	64,105
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property, plant and equipment	(33,960)	(28,747)
Purchases of securities	(1,822)	(12,049)
Sales and maturities of securities	2,955	19,986
Investments, net of return of capital, in equity method investees - payments	(9,800)
Investments, net of return of capital, in equity method investees - proceeds		211
Proceeds from asset disposals	249	140
Other, net	997	(24)
NET CASH USED IN INVESTING ACTIVITIES	(41,381)	(20,483)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings of long-term debt	700,000	73,600
Repayments of long-term debt	(509,968)	(87,344)
Payment of debt issuance costs	(8,197)	0
Dividends paid to common shareholders	(32,063)	(20,139)
Exercise of stock options	3,018	14,608
Cash paid for shares withheld to satisfy employee taxes	(4,710)	(7,045)
Other	(352)	(266)
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	147,728	(26,586)
EFFECTS OF EXCHANGE RATE CHANGES ON CASH	(10,660)	6,294
TOTAL INCREASE IN CASH AND CASH EQUIVALENTS AND RESTRICTED CASH AND CASH EQUIVALENTS	112,997	23,330
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	213,144	134,600
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH AND CASH EQUIVALENTS AT END OF PERIOD	326,141	157,930
Cash paid during the period for:
Interest	7,625	7,049
Income taxes (net of refunds)	49,848	33,997
SCHEDULE OF NON-CASH INVESTING ACTIVITY:
Accrued capital expenditures included in accounts payable	$ 8,775	$ 3,886

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES 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, 2017 (our " 2017 10-K"). We have included all adjustments, in the opinion of management, consisting only of normal recurring adjustments, necessary for a fair presentation. 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, 2018 and for the three and six months ended June 30, 2018 related to recently adopted accounting standards. 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. Reportable Segments We operate in three reportable segments: Nuclear Operations Group, Nuclear Services Group and Nuclear Power Group. Our reportable segments are further described as follows: • Our Nuclear Operations Group segment manufactures naval nuclear reactors for the Naval Nuclear Propulsion Program for use in U.S. Navy 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 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. Our Nuclear Services Group segment also provides inspection and maintenance services primarily for the U.S. commercial nuclear industry including steam generator and heat exchanger inspection services, high pressure water lancing, non-destructive examination and customized tooling solutions. This segment also offers complete advanced fuel and reactor engineering, licensing and manufacturing services for new advanced nuclear reactors. • Our Nuclear Power Group segment fabricates 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, for nuclear utility customers. BWXT has supplied the nuclear industry with more than 1,300 large, heavy components worldwide and is the only heavy nuclear component, N-Stamp certified 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. See Note 9 for financial information about our segments. Operating results for the three and six months ended June 30, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 . For further information, refer to the consolidated financial statements and the related footnotes included in our 2017 10-K. Acquisition of Sotera Health LLC's Nordion Medical Isotope Business On April 17, 2018, we signed a definitive agreement to acquire Sotera Health LLC's Nordion medical isotope business. Nordion's medical radioisotopes business is a leading global manufacturer and supplier of critical medical isotopes and radiopharmaceuticals for research, diagnostic and therapeutic uses. Its customers include radiopharmaceutical companies, hospitals and radiopharmacies. Its primary operations are located in Kanata, Ontario and Vancouver, British Columbia. This acquisition was completed on July 30, 2018 and will allow us to accelerate our entry into the medical radioisotope market by adding licensed infrastructure, approximately 150 highly trained and experienced personnel and two production centers. Beginning in the third quarter of 2018, this business will be reported as part of our Nuclear Power Group segment. Deconsolidation of Generation mPower LLC On March 2, 2016, we entered into a framework agreement with Bechtel Power Corporation ("Bechtel"), BWXT Modular Reactors, LLC and BDC NexGen Power, LLC for the potential restructuring and restart of our mPower small modular reactor program (the "Framework Agreement"). As a result of entering into the Framework Agreement, we deconsolidated Generation mPower LLC ("GmP") from our financial statements as of the date of the Framework Agreement and recognized a $30.0 million loss contingency, which was ultimately paid to Bechtel in the first quarter of 2017 following the receipt of Bechtel's notice that the mPower program would not be restarted. 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 Financial Accounting Standards Board ("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 (percentage-of-completion basis). 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 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. Accumulated Other Comprehensive Income The components of Accumulated other comprehensive income included in Stockholders' Equity are as follows: June 30, December 31, (In thousands) Currency translation adjustments $ 6,415 $ 13,148 Net unrealized gain on derivative financial instruments 384 353 Unrecognized prior service cost on benefit obligations (5,452 ) (6,237 ) Net unrealized gain (loss) on available-for-sale investments (99 ) 2,190 Accumulated other comprehensive income $ 1,248 $ 9,454 Upon adopting the FASB update to the Topic Financial Instruments , we reclassified $2.2 million of net unrealized gains on available-for-sale investments from Accumulated other comprehensive income to Retained earnings on January 1, 2018. The amounts reclassified out of Accumulated other comprehensive income by component and the affected condensed consolidated statements of income line items are as follows: Three Months Ended Six Months Ended 2018 2017 2018 2017 Accumulated Other Comprehensive Income (Loss) Component Recognized (In thousands) Line Item Presented Realized gain (loss) on derivative financial instruments $ 7 $ (9 ) $ (4 ) $ (13 ) Revenues (92 ) 237 28 291 Cost of operations (85 ) 228 24 278 Total before tax 21 (58 ) (9 ) (71 ) Provision for Income Taxes $ (64 ) $ 170 $ 15 $ 207 Net Income Amortization of prior service cost on benefit obligations $ (488 ) $ (446 ) $ (993 ) $ (892 ) Other – net 25 157 208 313 Provision for Income Taxes $ (463 ) $ (289 ) $ (785 ) $ (579 ) Net Income Realized gain on investments $ — $ 126 $ — $ 148 Other – net — (6 ) — (14 ) Provision for Income Taxes $ — $ 120 $ — $ 134 Net Income Total reclassification for the period $ (527 ) $ 1 $ (770 ) $ (238 ) Inventories At June 30, 2018 and December 31, 2017 , included in Other current assets, we had inventories totaling $11.7 million and $8.6 million , respectively, consisting entirely of raw materials and supplies. Deferred Debt Issuance Costs We have included deferred debt issuance costs in the condensed consolidated balance sheets as a direct deduction from the carrying amount of our Long-Term Debt. We amortize deferred debt issuance costs as interest expense over the life of the related debt. The following summarizes the changes in the carrying amount of our deferred debt issuance costs. Six Months Ended 2018 2017 (In thousands) Balance at beginning of period $ 4,202 $ 5,892 Additions 9,443 — Interest expense (1) (3,273 ) (850 ) Balance at end of period $ 10,372 $ 5,042 (1) Includes the recognition of prior deferred debt issuance costs associated with the Former Credit Facility of $2.4 million for the six months ended June 30, 2018 . Restricted Cash and Cash Equivalents At June 30, 2018 , we had restricted cash and cash equivalents totaling $8.5 million , $2.6 million of which was held for future decommissioning of facilities (which is included in Other Assets on our condensed consolidated balance sheets) and $5.9 million of which was held to meet reinsurance reserve requirements of our captive insurer. The following table provides a reconciliation of cash and cash equivalents and restricted cash and cash equivalents within our condensed consolidated balance sheets to the totals presented in our condensed consolidated statement of cash flows: June 30, December 31, (In thousands) Cash and cash equivalents $ 317,624 $ 203,404 Restricted cash and cash equivalents 5,870 7,105 Restricted cash and cash equivalents included in Other Assets 2,647 2,635 Total cash and cash equivalents and restricted cash and cash equivalents as presented in our condensed consolidated statement of cash flows $ 326,141 $ 213,144 Warranty Expense We accrue estimated expense, included in Cost of operations on our condensed consolidated statements of income, to satisfy contractual warranty requirements when we recognize the associated revenue on the related contracts. In addition, we record specific provisions or reductions where we expect the actual warranty costs to significantly differ from the accrued estimates. Such changes could have a material effect on our consolidated financial condition, results of operations and cash flows. The following summarizes the changes in the carrying amount of our Accrued warranty expense: Six Months Ended 2018 2017 (In thousands) Balance at beginning of period $ 13,428 $ 11,477 Additions 810 667 Expirations and other changes (709 ) (84 ) Payments (347 ) (16 ) Translation (360 ) 173 Balance at end of period $ 12,822 $ 12,217 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 changes in our mix of income within these jurisdictions, can contribute to shifts in our effective tax rate from period to period. On December 22, 2017, the Tax Cuts and Jobs Act (the "Act") was enacted, making significant changes to existing U.S. tax laws that impact BWXT, including, but not limited to, a reduction to the U.S. corporate income tax rate from 35% to 21% for tax years beginning after December 31, 2017, the taxation of global intangible low-taxed income ("GILTI") and additional deduction limitations related to executive compensation. We recognized the income tax effects of the Act within our condensed consolidated financial statements in accordance with FASB Topic Income Taxes . Our Canadian operations continue to be subject to tax at a local statutory rate of approximately 25% . Our effective tax rate for the three months ended June 30, 2018 was 23.3% as compared to 30.6% for the three months ended June 30, 2017 . Our effective tax rate for the six months ended June 30, 2018 was 22.6% as compared to 30.6% for the six months ended June 30, 2017 . The effective tax rates for the three and six months ended June 30, 2018 were slightly higher than the U.S. corporate income tax rate of 21% primarily due to state income taxes within the U.S. and the unfavorable rate differential associated with our Canadian earnings. Our effective tax rate for the three months ended June 30, 2018 and 2017 was favorably impacted by benefits recognized for excess tax benefits related to employee share-based payments of $0.2 million and $2.6 million , respectively. Our effective tax rate for the six months ended June 30, 2018 and 2017 was favorably impacted by benefits recognized for excess tax benefits related to employee share-based payments of $2.4 million and $4.9 million , respectively. As of June 30, 2018 , we had gross unrecognized tax benefits of $0.8 million (exclusive of interest and federal and state benefits), all of which would reduce our effective tax rate if recognized. New Accounting Standards In February 2016, the FASB issued an update to the Topic Leases , which supersedes the lease reporting requirements in Topic Leases (previously "FAS 13"). This update requires that a lessee recognize on its balance sheet the assets and liabilities for all leases with lease terms of more than 12 months, along with additional qualitative and quantitative disclosures. The effect of leases in a consolidated statement of income and a consolidated statement of cash flows is expected to be largely unchanged. Accounting by lessors was not significantly impacted by this update. This update will be effective for us in 2019, with early adoption permitted. We expect to adopt the provisions in this update effective January 1, 2019 using the modified retrospective approach. We do not anticipate a material impact on our financial statements upon adoption.

Revenue Recognition

Revenue Recognition	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue Recognition	REVENUE RECOGNITION The initial impact of the adoption of the FASB Topic Revenue from Contracts with Customers , which was recognized in a cumulative catch-up adjustment on January 1, 2018, is illustrated below: January 1, December 31, 2018 2017 (In thousands) Assets: Contracts in progress $ 260,932 $ 420,628 Deferred Income Taxes $ 85,193 $ 86,740 Liabilities: Accrued liabilities – other $ 66,371 $ 64,738 Advance billings on contracts $ 73,390 $ 246,192 Stockholders' Equity: Retained earnings $ 1,000,578 $ 990,652 Within our Nuclear Operations Group segment, we continue to recognize revenue over time and now measure progress on performance obligations using a cost-to-cost method. Historically, we utilized man-hours or a cost-to-cost method to measure progress on certain performance obligations within this segment. The performance obligations identified for recognizing revenue are similar to our historical units of account. As a result of the change to a cost-to-cost method, the timing of revenue recognition on affected contracts, in the aggregate, results in the recognition of revenue and cost of operations earlier in the process of satisfying performance obligations. This change impacted the life-to-date revenue and cost of operations recognized on performance obligations, and the adjustment to capture the impact of the new revenue recognition standard was recorded as a cumulative catch-up adjustment in Retained earnings. The new standard also resulted in a reduction in both our Contracts in progress and Advance billings on contracts account balances as a result of measuring the asset and liability at the contract level. Historically, contract assets and liabilities were measured at the unit of account, which we concluded was at a lower level than that of the contract. The impact of the adoption of the new revenue standard on our Nuclear Power Group and Nuclear Services Group segments was not material. Contracts and Revenue Recognition Nuclear Operations Group Our Nuclear Operations Group segment recognizes revenue over time for the manufacturing of naval nuclear reactor components and fuel, submarine missile launch tubes and the downblending of high-enriched uranium. Certain of our contracts contain two or more different types of components, each of which we identify as a separate performance obligation. We recognize revenue using a cost-to-cost method to measure progress as control is continually transferred to the customer as we incur costs on the performance obligations. We allocate revenue to the individual performance obligations within contracts with multiple performance obligations based on the stand-alone selling price of the individual performance obligations. Our fixed-price incentive fee contracts include incentives that we concluded to be variable consideration. The amount of the variable consideration to which we are entitled is dependent on our actual costs incurred on the performance obligation compared to the target costs for that performance obligation and subject to incentive price revisions included within the contracts. We include these incentive fees in revenue when there is sufficient evidence to determine that the variable consideration is not constrained. The remaining contracts typically have immaterial amounts of variable consideration and have a single performance obligation. Our estimates of variable consideration and total estimated costs at completion are determined through a detailed process based on historical performance and our expertise using the most likely method. Variations from estimated contract performance could result in a material effect on our financial condition and results of operations in future periods. Our Nuclear Operations Group segment's contracts allow for billings as costs are incurred, subject to certain retainages on our fixed-price incentive fee contracts, that require milestones to be reached for the remaining consideration to be paid. Nuclear Services Group Our contracts within our Nuclear Services Group segment are primarily cost-plus service contracts on which we recognize revenue over time based on a cost-to-cost method, which is consistent with the structure of the billings associated with these contracts. Ownership continuously transfers to the customer as we perform the services. The contracts within this segment do not contain significant variable consideration and contain a single performance obligation. Certain of these contracts contain assurance warranties and/or provisions for liquidated damages, which are expected to have an immaterial impact on the contracts based on our historical experience. Nuclear Power Group Our Nuclear Power Group segment recognizes revenue over time using a cost-to-cost method for the manufacturing of large components, non-standard parts, fuel bundles and service contracts as control continually transfers to the customers. For standard parts, revenue is recognized at the point in time control transfers to the customer, which is consistent with the transfer of ownership. This segment generates revenue primarily from firm-fixed-price contracts that do not contain variable consideration as well as time-and-materials based contracts. Certain of these contracts contain assurance warranties and/or provisions for liquidated damages, which are expected to have an immaterial impact to the contracts based on our historical experience. We are entitled to payment on the majority of our Nuclear Power Group segment contracts when we achieve certain milestones related to our progress. Disaggregated Revenues Revenues by geographical area and customer type are as follows: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Nuclear Nuclear Nuclear Total Nuclear Nuclear Nuclear Total (In thousands) United States: Government $ 327,896 $ 28,174 $ — $ 356,070 $ 644,527 $ 54,055 $ — $ 698,582 Non-Government 3,849 3,910 327 8,086 3,849 7,087 587 11,523 $ 331,745 $ 32,084 $ 327 $ 364,156 $ 648,376 $ 61,142 $ 587 $ 710,105 Canada: Government $ — $ — $ — $ — $ — $ — $ — $ — Non-Government — 510 64,743 65,253 — 1,485 147,068 148,553 $ — $ 510 $ 64,743 $ 65,253 $ — $ 1,485 $ 147,068 $ 148,553 Other: Government $ — $ — $ — $ — $ — $ — $ — $ — Non-Government 395 2 10,627 11,024 395 2 40,858 41,255 $ 395 $ 2 $ 10,627 $ 11,024 $ 395 $ 2 $ 40,858 $ 41,255 Segment Revenues $ 332,140 $ 32,596 $ 75,697 440,433 $ 648,771 $ 62,629 $ 188,513 899,913 Adjustments and Eliminations (1,512 ) (3,529 ) Revenues $ 438,921 $ 896,384 Revenues by timing of transfer of goods or services are as follows: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Nuclear Nuclear Nuclear Total Nuclear Nuclear Nuclear Total (In thousands) Over-time $ 332,140 $ 32,596 $ 69,324 $ 434,060 $ 648,771 $ 62,629 $ 174,433 $ 885,833 Point-in-time — — 6,373 6,373 — — 14,080 14,080 Segment Revenues $ 332,140 $ 32,596 $ 75,697 440,433 $ 648,771 $ 62,629 $ 188,513 899,913 Adjustments and Eliminations (1,512 ) (3,529 ) Revenues $ 438,921 $ 896,384 Revenues by contract type are as follows: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Nuclear Nuclear Nuclear Total Nuclear Nuclear Nuclear Total (In thousands) Fixed-Price Incentive Fee $ 258,150 $ — $ 5,589 $ 263,739 $ 507,390 $ — $ 9,617 $ 517,007 Firm-Fixed-Price 52,472 5,632 44,302 102,406 99,530 11,042 118,584 229,156 Cost-Plus Fee 21,450 26,086 — 47,536 41,683 50,039 45 91,767 Time-and-Materials 68 878 25,806 26,752 168 1,548 60,267 61,983 Segment Revenues $ 332,140 $ 32,596 $ 75,697 440,433 $ 648,771 $ 62,629 $ 188,513 899,913 Adjustments and Eliminations (1,512 ) (3,529 ) Revenues $ 438,921 $ 896,384 Performance Obligations As we progress on our contracts and the underlying performance obligations for which we recognize revenue over time, we refine our estimates of variable consideration and total estimated costs at completion, which impact the overall profitability on our contracts and performance obligations. Changes in these estimates result in the recognition of cumulative catch-up adjustments that impact our revenue and/or costs of contracts. During the six months ended June 30, 2018 , we recognized net favorable changes in estimates that resulted in increases in revenue of $14.5 million . During the three months ended June 30, 2018, we identified rework issues related to non-nuclear components being produced within our Nuclear Operations Group segment. As we work to resolve these issues, we do not expect additional costs to have a material adverse effect on our consolidated financial condition, results of operations or cash flows. Contract Assets and Liabilities We include revenues and related costs incurred, plus accumulated contract costs that exceed amounts invoiced to customers under the terms of the contracts, in Contracts in progress. We include in Advance billings on contracts billings that exceed accumulated contract costs and revenues and costs recognized over time. Most long-term contracts contain provisions for progress payments. Our unbilled receivables do not contain an allowance for credit losses as we expect to invoice customers and collect all amounts for unbilled revenues. Changes in Contracts in progress and Advance billings on contracts are primarily driven by differences in the timing of revenue recognition and billings to our customers. During the six months ended June 30, 2018 , our unbilled receivables increased $56.2 million , primarily as a result of revenue in excess of billings on certain firm-fixed-price contracts within our Nuclear Operations Group segment and the timing of milestone billings on large components and contracts started in 2018 within our Nuclear Power Group segment. Our fixed-price incentive fee contracts for our Nuclear Operations Group segment include provisions that result in an increase in retainages on contracts during the first and third quarters of the year, with larger payments made during the second and fourth quarters. Retainages also vary as a result of timing differences between incurring costs and achieving milestones that allow us to recover these amounts. This resulted in an increase in retainages on contracts from January 1 to June 30, 2018 as shown below: June 30, January 1, 2018 2018 (In thousands) Included in Contracts in progress: Unbilled receivables $ 306,535 $ 250,325 Included in Accounts receivable – trade, net: Retainages $ 96,731 $ 82,801 Included in Other Assets: Retainages $ 1,626 $ 1,669 Advance billings on contracts $ 77,775 $ 73,390 During the six months ended June 30, 2018 , we recognized $44.7 million of revenue that was in Advance billings on contracts at January 1, 2018. Remaining Performance Obligations Remaining performance obligations represent the dollar amount of revenue we expect to recognize in the future from performance obligations on contracts previously awarded and in progress. Of the June 30, 2018 remaining performance obligations on our contracts with customers, we expect to recognize revenues as follows: 2018 2019 Thereafter Total (In approximate millions) Nuclear Operations Group $ 630 $ 798 $ 1,258 $ 2,686 Nuclear Services Group 35 3 6 44 Nuclear Power Group 141 143 599 883 Total Remaining Performance Obligations $ 806 $ 944 $ 1,863 $ 3,613 Historical Method Prior to the adoption of FASB Topic Revenue from Contracts with Customers , we accounted for revenue under previous GAAP. In accordance with our adoption of the new revenue recognition standard utilizing the modified retrospective approach, we are required to disclose the impact on our financial statements on a line item basis. A comparison of certain line items in our condensed consolidated balance sheet is shown below: June 30, 2018 Current Method Historical Method (In thousands) Assets: Contracts in progress $ 317,405 $ 348,762 Deferred Income Taxes $ 84,868 $ 85,295 Liabilities: Accrued liabilities – other $ 48,377 $ 45,572 Advance billings on contracts $ 77,775 $ 121,902 Stockholders' Equity: Retained earnings $ 1,097,665 $ 1,088,127 Differences in the amounts above are primarily the result of the initial adoption of the new revenue recognition standard. Additional differences were caused by revenue under the current method being $9.2 million lower than the historical method as discussed below. A comparison of certain line items in our condensed consolidated statements of income is shown below: Three Months Ended Six Months Ended Current Method Historical Method Current Method Historical Method (In thousands) Revenues $ 438,921 $ 440,103 $ 896,384 $ 905,633 Cost of operations $ 318,209 $ 319,945 $ 645,573 $ 654,487 Operating Income $ 71,549 $ 70,995 $ 151,437 $ 151,772 Provision for Income Taxes $ 18,493 $ 18,311 $ 37,096 $ 37,043 Net Income $ 60,734 $ 60,362 $ 127,147 $ 127,535 We recognized $1.2 million and $9.2 million less revenue under the current method compared to the historical method for the three and six months ended June 30, 2018 , respectively. This was primarily driven by less progress being achieved on contracts as a result of using a cost-to-cost method for measuring progress under the current method as compared to man-hours or units of output under our historical method.

Long-term Debt

Long-term Debt	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Long-term Debt	LONG-TERM DEBT Our Long-Term Debt consists of the following: June 30, December 31, (In thousands) Long-Term Debt: Senior Notes $ 400,000 $ — New Credit Facility 291,128 — Former Credit Facility — 513,131 Less: Amounts due within one year 14,556 27,870 Long-term debt, gross 676,572 485,261 Less: Deferred debt issuance costs 10,372 4,202 Long-term debt $ 666,200 $ 481,059 Maturities of long-term debt subsequent to June 30, 2018 are as follows: 2018 – $7.3 million ; 2019 – $14.6 million ; 2020 – $14.6 million ; 2021 – $14.6 million ; 2022 – $14.6 million ; 2023 – $225.6 million ; and thereafter – $400.0 million . On May 24, 2018, we and certain of our subsidiaries entered into a credit agreement (the "New Credit Facility") with Wells Fargo Bank, N.A., as administrative agent, and the other lenders party thereto. We also issued notes pursuant to an indenture among the Company, certain of our subsidiaries, as guarantors, and U.S. Bank National Association, as trustee. In connection with the closing of the New Credit Facility and the issuance of the notes, we concurrently repaid all outstanding debt obligations and terminated our credit agreement dated as of May 11, 2015, as amended, among the Company, certain of our subsidiaries, Bank of America, N.A., as administrative agent, and the other lenders party thereto (the "Former Credit Facility"). The Former Credit Facility consisted of (1) a $400.0 million revolving credit facility, (2) a $300.0 million term loan facility, (3) a $137.5 million (U.S. dollar equivalent) Canadian dollar term loan facility, and (4) a $112.5 million term loan facility. Credit Facility The New Credit Facility includes a $500.0 million senior secured revolving credit facility (the "New Revolving Credit Facility"), a $50.0 million U.S. dollar senior secured term loan A made available to the Company (the "New USD Term Loan") and a $250.0 million (U.S. dollar equivalent) Canadian dollar senior secured term loan A made available to BWXT Canada Ltd. (the "New CAD Term Loan"). All obligations under the New Credit Facility are scheduled to mature on May 24, 2023. The proceeds of loans under the New Credit Facility are available for working capital needs and other general corporate purposes. The New Credit Facility allows for additional parties to become lenders and, subject to certain conditions, for the increase of the commitments under the New Revolving Credit Facility, the New USD Term Loan or the New CAD Term Loan, subject to an aggregate maximum for all additional commitments of (1) the greater of (a) $250 million and (b) 65% of EBITDA, as defined in the New Credit Facility, for the last four full fiscal quarters, plus (2) all voluntary prepayments of term loans, plus (3) additional amounts provided the Company is in compliance with a pro forma first lien leverage ratio test of less than or equal to 2.50 to 1.00 . The Company's obligations under the New Credit Facility are guaranteed, subject to certain exceptions, by substantially all of the Company's present and future wholly owned domestic restricted subsidiaries (other than its captive insurance subsidiary and the domestic holding company of its Canadian subsidiaries). The obligations of BWXT Canada Ltd. under the New Credit Facility are guaranteed, subject to certain exceptions, by (1) substantially all of the present and future wholly owned Canadian restricted subsidiaries of BWXT Canada Ltd., (2) substantially all of the Company's present and future wholly owned domestic restricted subsidiaries (other than its captive insurance subsidiary and the domestic holding company of its Canadian subsidiaries), (3) BWXT Canada Holdings Corp. and (4) BWXT ITG Canada Inc. The New Credit Facility is secured by first-priority liens on certain assets owned by the Company (other than its subsidiaries comprising its Nuclear Operations Group segment and a portion of its Nuclear Services Group segment); provided that (1) the Company's domestic obligations are only secured by assets and property of the domestic loan parties and (2) the obligations of BWXT Canada Ltd. and the Canadian guarantors are secured by assets and property of the Canadian guarantors and the domestic loan parties. The New Credit Facility requires interest payments on revolving loans on a periodic basis until maturity. We will be required to make quarterly amortization payments on the New USD Term Loan and the New CAD Term Loan in an amount equal to 1.25% of the initial aggregate principal amount of each term loan beginning in the third quarter of 2018. We may prepay all loans under the New Credit Facility at any time without premium or penalty (other than customary Eurocurrency breakage costs), subject to notice requirements. The New Credit Facility includes financial covenants that are tested on a quarterly basis, based on the rolling four-quarter period that ends on the last day of each fiscal quarter. The maximum permitted leverage ratio is 4.00 to 1.00 , which may be increased to 4.50 to 1.00 for up to four consecutive fiscal quarters after a material acquisition. The minimum consolidated interest coverage ratio is 3.00 to 1.00 . In addition, the New Credit Facility contains various restrictive covenants, including with respect to debt, liens, investments, mergers, acquisitions, dividends, equity repurchases and asset sales. As of June 30, 2018 , we were in compliance with all covenants set forth in the New Credit Facility. Outstanding loans under the New Credit Facility bear interest at our option at either (1) the Eurocurrency rate plus a margin ranging from 1.25% to 2.00% per year or (2) the base rate or Canadian index rate, as applicable (described in the New Credit Facility as the highest of (a) with respect to the base rate only, the federal funds rate plus 0.50% , (b) the one-month Eurocurrency rate plus 1.0% and (c) the administrative agent's prime rate or the Canadian prime rate, as applicable), plus, in each case, a margin ranging from 0.25% to 1.00% per year. We are charged a commitment fee on the unused portion of the New Revolving Credit Facility, and that fee ranges from 0.150% to 0.275% per year. Additionally, we are charged a letter of credit fee of between 1.25% and 2.00% per year with respect to the amount of each financial letter of credit issued under the New Credit Facility, and a letter of credit fee of between 0.75% and 1.20% per year is charged with respect to the amount of each performance letter of credit issued under the New Credit Facility. The applicable margin for loans, the commitment fee and the letter of credit fees set forth above will vary quarterly based on our leverage ratio. Based on the leverage ratio applicable at June 30, 2018 , the margin for Eurocurrency rate and base rate or Canadian index rate loans was 1.375% and 0.375% , respectively, the letter of credit fee for financial letters of credit and performance letters of credit was 1.375% and 0.825% , respectively, and the commitment fee for the unused portion of the New Revolving Credit Facility was 0.175% . As of June 30, 2018 , borrowings outstanding totaled $291.1 million and $0.0 million under our term loans and revolving line of credit, respectively, and letters of credit issued under the New Credit Facility totaled $71.5 million . As a result, we had $428.5 million available for borrowings or to meet letter of credit requirements as of June 30, 2018 . As of June 30, 2018 , the weighted-average interest rate on outstanding borrowings under our New Credit Facility was 3.09% . The New Credit Facility generally includes customary events of default for a secured credit facility, some of which allow for an opportunity to cure. Under the New Credit Facility, (1) if an event of default relating to bankruptcy or other insolvency events occurs, all related obligations will immediately become due and payable, (2) if any other event of default exists, the lenders will be permitted to accelerate the maturity of the related obligations outstanding and (3) if any event of default exists, the lenders will be permitted to terminate their commitments thereunder and exercise other rights and remedies, including the commencement of foreclosure or other actions against the collateral. If any default occurs under the New Credit Facility, or if we are unable to make any of the representations and warranties in the New Credit Facility, we will be unable to borrow funds or have letters of credit issued under the New Credit Facility. Senior Notes The Company issued $400.0 million aggregate principal amount of its 5.375% senior notes due 2026 (the "Senior Notes") pursuant to an indenture dated May 24, 2018 (the "Indenture"), among the Company, the guarantors and U.S. Bank National Association, as trustee. The Senior Notes are guaranteed by each of the Company's present and future direct and indirect wholly owned domestic subsidiaries that is a guarantor under the New Credit Facility. Interest on the Senior Notes is payable semi-annually in cash in arrears on January 15 and July 15 of each year, commencing on July 15, 2018, at a rate of 5.375% per annum. The Senior Notes will mature on July 15, 2026. The Company may redeem the Senior Notes, in whole or in part, at any time on or after July 15, 2021 at established redemption prices. At any time prior to July 15, 2021, the Company may also redeem up to 40% of the Senior Notes with net cash proceeds of certain equity offerings at a redemption price equal to 105.375% of the principal amount of the Senior Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date. In addition, at any time prior to July 15, 2021, the Company may redeem the Senior Notes, in whole or in part, at a redemption price equal to 100% of the principal amount of the Senior Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date plus an applicable "make-whole" premium. The Indenture contains customary events of default, including, among other things, payment default, failure to comply with covenants or agreements contained in the Indenture or the Senior Notes and certain provisions related to bankruptcy events. The Indenture also contains customary negative covenants. As of June 30, 2018 , we were in compliance with all covenants and agreements set forth in the Indenture and the Senior Notes.

Pension Plans and Postretiremen

Pension Plans and Postretirement Benefits	6 Months Ended
	Jun. 30, 2018
Defined Benefit Plan [Abstract]
Pension Plans and Postretirement Benefits	PENSION PLANS AND POSTRETIREMENT BENEFITS We record the service cost component of net periodic benefit cost within Operating income on our condensed consolidated statements of income. For the three months ended June 30, 2018 and 2017 , these amounts were $2.6 million and $2.3 million , respectively. For the six months ended June 30, 2018 and 2017 , these amounts were $5.1 million and $4.6 million , respectively. All other components of net periodic benefit cost are included in Other – net within the condensed consolidated statements of income. For the three months ended June 30, 2018 and 2017 , these amounts were $(8.8) million and $(6.9) million respectively. For the six months ended June 30, 2018 and 2017 , these amounts were $(17.7) million and $(13.9) million , respectively. Components of net periodic benefit cost included in net income are as follows: Pension Benefits Other Benefits Three Months Ended Six Months Ended Three Months Ended Six Months Ended 2018 2017 2018 2017 2018 2017 2018 2017 (In thousands) Service cost $ 2,405 $ 2,145 $ 4,818 $ 4,296 $ 162 $ 153 $ 327 $ 307 Interest cost 12,307 13,495 24,650 27,008 351 538 900 1,078 Expected return on plan assets (21,553 ) (20,803 ) (43,178 ) (41,640 ) (399 ) (596 ) (1,033 ) (1,191 ) Amortization of prior service cost (credit) 550 525 1,100 1,050 (62 ) (78 ) (107 ) (157 ) Net periodic benefit (income) cost $ (6,291 ) $ (4,638 ) $ (12,610 ) $ (9,286 ) $ 52 $ 17 $ 87 $ 37 In July 2018, we completed the purchase of a group annuity contract to transfer certain domestic pension benefit obligations of approximately $240 million to an insurance company for approximately 1,300 retirees. This transaction will result in the recognition of pension settlement-related charges and net actuarial gains and losses related to an interim remeasurement of our domestic pension benefit obligation (Mark to Market Adjustment) during the quarter ending September 30, 2018.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES There were no material contingencies during the period covered by this Form 10-Q. For more information regarding commitments and contingencies, refer to Note 10 to the consolidated financial statements in Part II of our 2017 10-K, as updated by our Form 10-Q for the quarter ended March 31, 2018.

Derivative Financial Instrument

Derivative Financial Instruments	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
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 primarily to hedge our exposure associated with revenues or costs on our long-term contracts that are denominated in currencies other than our operating entities' functional currencies. In addition, we have entered into FX forward contracts to hedge our exposure on pending acquisitions. 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 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. Any ineffective portion of a derivative's change in fair value and any portion excluded from the assessment of effectiveness are immediately recognized in Other – net in our condensed consolidated statements of income. The gain or loss on a derivative instrument not designated as a hedging instrument is also immediately recognized in earnings. Gains and losses on derivative financial instruments that require immediate recognition are included as a component of Other – net in 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 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. At June 30, 2018 , we had deferred approximately $0.4 million of net gains on these derivative financial instruments in Accumulated other comprehensive income. Assuming market conditions continue, we expect to recognize the majority of this amount in the next 12 months. At June 30, 2018 , our derivative financial instruments consisted of FX forward contracts. The notional value of our FX forward contracts totaled $249.4 million at June 30, 2018 , with maturities extending to December 2021 . These instruments consist primarily of contracts to purchase or sell Canadian dollars. We are exposed to credit-related losses in the event of non-performance by counterparties to derivative financial instruments. We attempt to mitigate this risk by using major financial institutions with high credit ratings. Our counterparties have the benefit of the same collateral arrangements and covenants as described under our credit facility. The following tables summarize our derivative financial instruments at June 30, 2018 and December 31, 2017 : Asset and Liability Derivatives June 30, December 31, (In thousands) Derivatives Designated as Hedges: FX Forward Contracts: Location Accounts receivable – other $ 444 $ 250 Other Assets $ 468 $ 348 Accounts payable $ 219 $ 177 Other Liabilities $ 284 $ 93 Derivatives Not Designated as Hedges: FX Forward Contracts: Location Accounts receivable – other $ 5,000 $ — The effects of derivatives on our financial statements are outlined below: Three Months Ended Six Months Ended 2018 2017 2018 2017 (In thousands) Derivatives Designated as Hedges: Cash Flow Hedges: FX Forward Contracts: Amount of gain recognized in other comprehensive income $ (157 ) $ 551 $ 75 $ 927 Gain (loss) reclassified from accumulated other comprehensive income (loss) into earnings: effective portion Location Revenues $ 7 $ (9 ) $ (4 ) $ (13 ) Cost of operations $ (92 ) $ 237 $ 28 $ 291 Derivatives Not Designated as Hedges: FX Forward Contracts: Gain (loss) recognized in income Location Other – net $ 5,997 $ — $ 5,997 $ —

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Investments The following is a summary of our investments measured at fair value at June 30, 2018 : Total Level 1 Level 2 Level 3 (In thousands) Equity securities Equities $ 2,366 $ — $ 2,366 $ — Mutual funds 4,933 — 4,933 — Available-for-sale securities U.S. Government and agency securities 1,824 1,824 — — Corporate bonds 1,493 1,493 — — Asset-backed securities and collateralized mortgage obligations 140 — 140 — Total $ 10,756 $ 3,317 $ 7,439 $ — The following is a summary of our investments measured at fair value at December 31, 2017 : Total Level 1 Level 2 Level 3 (In thousands) Available-for-sale securities U.S. Government and agency securities $ 1,299 $ 1,299 $ — $ — Corporate bonds 3,169 1,534 1,635 — Equities 2,759 — 2,759 — Mutual funds 4,847 — 4,847 — Asset-backed securities and collateralized mortgage obligations 161 — 161 — Total $ 12,235 $ 2,833 $ 9,402 $ — We estimate the fair value of investments based on quoted market prices. For investments for which there are no quoted market prices, we derive fair values from available yield curves for investments of similar quality and terms. Derivatives Level 2 derivative assets and liabilities currently consist of FX forward contracts. Where applicable, the value of these derivative assets and liabilities is computed by discounting the projected future cash flow amounts to present value using market-based observable inputs, including FX forward and spot rates, interest rates and counterparty performance risk adjustments. At June 30, 2018 and December 31, 2017 , we had forward contracts outstanding to purchase or sell Canadian dollars, with a total fair value of $5.4 million and $0.3 million , respectively. Other Financial Instruments We used the following methods and assumptions in estimating our fair value disclosures for our other financial instruments, as follows: Cash and cash equivalents and restricted cash and cash equivalents . The carrying amounts that we have reported in the accompanying condensed consolidated balance sheets for Cash and cash equivalents and Restricted cash and cash equivalents approximate their fair values due to their highly liquid nature. Long-term and short-term debt . We base the fair values of debt instruments on quoted market prices. Where quoted prices are not available, we base the fair values on the present value of future cash flows discounted at estimated borrowing rates for similar debt instruments or on estimated prices based on current yields for debt issues of similar quality and terms. The fair values of our debt instruments approximated their carrying values at June 30, 2018 and December 31, 2017 .

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION Stock-based compensation recognized for all of our plans for the three months ended June 30, 2018 and 2017 totaled $1.4 million and $4.0 million , respectively, with associated tax benefit totaling $0.3 million and $1.4 million , respectively. Stock-based compensation recognized for all of our plans for the six months ended June 30, 2018 and 2017 totaled $6.3 million and $8.7 million , respectively, with associated tax benefit totaling $1.2 million and $3.0 million , respectively.

Segment Reporting

Segment Reporting	6 Months Ended
	Jun. 30, 2018
Segment Reporting [Abstract]
Segment Reporting	SEGMENT REPORTING As described in Note 1 , our operations are assessed based on three reportable segments. An analysis of our operations by reportable segment is as follows: Three Months Ended Six Months Ended 2018 2017 2018 2017 (In thousands) REVENUES: Nuclear Operations Group $ 332,140 $ 312,866 $ 648,771 $ 637,947 Nuclear Services Group 32,596 44,785 62,629 72,639 Nuclear Power Group 75,697 54,569 188,513 132,243 Adjustments and Eliminations (1) (1,512 ) (2,209 ) (3,529 ) (4,589 ) $ 438,921 $ 410,011 $ 896,384 $ 838,240 (1) Segment revenues are net of the following intersegment transfers and other adjustments: Nuclear Operations Group Transfers $ (841 ) $ (205 ) $ (1,980 ) $ (400 ) Nuclear Services Group Transfers (702 ) (1,913 ) (1,540 ) (4,070 ) Nuclear Power Group Transfers 31 (91 ) (9 ) (119 ) $ (1,512 ) $ (2,209 ) $ (3,529 ) $ (4,589 ) OPERATING INCOME: Nuclear Operations Group $ 67,046 $ 69,295 $ 134,703 $ 137,044 Nuclear Services Group 3,511 15,399 4,688 15,801 Nuclear Power Group 7,810 5,712 29,574 18,668 Other (4,357 ) (1,070 ) (8,400 ) (2,682 ) $ 74,010 $ 89,336 $ 160,565 $ 168,831 Unallocated Corporate (2) (2,461 ) (3,908 ) (9,128 ) (7,131 ) Total Operating Income $ 71,549 $ 85,428 $ 151,437 $ 161,700 Other Income (Expense) : Interest income 441 211 1,219 348 Interest expense (7,869 ) (3,906 ) (11,429 ) (7,423 ) Other – net 15,106 6,749 23,016 14,235 Total Other Income (Expense) 7,678 3,054 12,806 7,160 Income before Provision for Income Taxes $ 79,227 $ 88,482 $ 164,243 $ 168,860 (2) Unallocated corporate includes general corporate overhead not allocated to segments.

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE The following table sets forth the computation of basic and diluted earnings per share: Three Months Ended Six Months Ended 2018 2017 2018 2017 (In thousands, except share and per share amounts) Basic: Net Income Attributable to BWX Technologies, Inc. $ 60,663 $ 61,263 $ 127,104 $ 116,982 Weighted-average common shares 99,681,580 99,166,205 99,603,884 99,305,558 Basic earnings per common share $ 0.61 $ 0.62 $ 1.28 $ 1.18 Diluted: Net Income Attributable to BWX Technologies, Inc. $ 60,663 $ 61,263 $ 127,104 $ 116,982 Weighted-average common shares (basic) 99,681,580 99,166,205 99,603,884 99,305,558 Effect of dilutive securities: Stock options, restricted stock units and performance shares (1) 890,157 984,721 938,130 1,115,390 Adjusted weighted-average common shares 100,571,737 100,150,926 100,542,014 100,420,948 Diluted earnings per common share $ 0.60 $ 0.61 $ 1.26 $ 1.16 (1) At June 30, 2018 and 2017 , none of our shares were antidilutive.

Basis of Presentation and Sig20

Basis of Presentation and Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2018
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, 2017 (our " 2017 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, 2018 and for the three and six months ended June 30, 2018 related to recently adopted accounting standards. 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.
Reportable Segments	Reportable Segments We operate in three reportable segments: Nuclear Operations Group, Nuclear Services Group and Nuclear Power Group. Our reportable segments are further described as follows: • Our Nuclear Operations Group segment manufactures naval nuclear reactors for the Naval Nuclear Propulsion Program for use in U.S. Navy 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 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. Our Nuclear Services Group segment also provides inspection and maintenance services primarily for the U.S. commercial nuclear industry including steam generator and heat exchanger inspection services, high pressure water lancing, non-destructive examination and customized tooling solutions. This segment also offers complete advanced fuel and reactor engineering, licensing and manufacturing services for new advanced nuclear reactors. • Our Nuclear Power Group segment fabricates 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, for nuclear utility customers. BWXT has supplied the nuclear industry with more than 1,300 large, heavy components worldwide and is the only heavy nuclear component, N-Stamp certified 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. See Note 9 for financial information about our segments. Operating results for the three and six months ended June 30, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 . For further information, refer to the consolidated financial statements and the related footnotes included in our 2017 10-K.
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 Financial Accounting Standards Board ("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 (percentage-of-completion basis). 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 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.
Inventories	Inventories At June 30, 2018 and December 31, 2017 , included in Other current assets, we had inventories totaling $11.7 million and $8.6 million , respectively, consisting entirely of raw materials and supplies.
Restricted Cash and Cash Equivalents	Restricted Cash and Cash Equivalents At June 30, 2018 , we had restricted cash and cash equivalents totaling $8.5 million , $2.6 million of which was held for future decommissioning of facilities (which is included in Other Assets on our condensed consolidated balance sheets) and $5.9 million of which was held to meet reinsurance reserve requirements of our captive insurer.
Warranty Expense	Warranty Expense We accrue estimated expense, included in Cost of operations on our condensed consolidated statements of income, to satisfy contractual warranty requirements when we recognize the associated revenue on the related contracts. In addition, we record specific provisions or reductions where we expect the actual warranty costs to significantly differ from the accrued estimates. Such changes could have a material effect on our consolidated financial condition, results of operations and cash flows.
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 changes in our mix of income within these jurisdictions, can contribute to shifts in our effective tax rate from period to period.
New Accounting Standards	New Accounting Standards In February 2016, the FASB issued an update to the Topic Leases , which supersedes the lease reporting requirements in Topic Leases (previously "FAS 13"). This update requires that a lessee recognize on its balance sheet the assets and liabilities for all leases with lease terms of more than 12 months, along with additional qualitative and quantitative disclosures. The effect of leases in a consolidated statement of income and a consolidated statement of cash flows is expected to be largely unchanged. Accounting by lessors was not significantly impacted by this update. This update will be effective for us in 2019, with early adoption permitted. We expect to adopt the provisions in this update effective January 1, 2019 using the modified retrospective approach. We do not anticipate a material impact on our financial statements upon adoption.

Basis of Presentation and Sig21

Basis of Presentation and Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Components of Accumulated Other Comprehensive Income	The components of Accumulated other comprehensive income included in Stockholders' Equity are as follows: June 30, December 31, (In thousands) Currency translation adjustments $ 6,415 $ 13,148 Net unrealized gain on derivative financial instruments 384 353 Unrecognized prior service cost on benefit obligations (5,452 ) (6,237 ) Net unrealized gain (loss) on available-for-sale investments (99 ) 2,190 Accumulated other comprehensive income $ 1,248 $ 9,454
Schedule of Amounts Reclassified from Accumulated Other Comprehensive Income	The amounts reclassified out of Accumulated other comprehensive income by component and the affected condensed consolidated statements of income line items are as follows: Three Months Ended Six Months Ended 2018 2017 2018 2017 Accumulated Other Comprehensive Income (Loss) Component Recognized (In thousands) Line Item Presented Realized gain (loss) on derivative financial instruments $ 7 $ (9 ) $ (4 ) $ (13 ) Revenues (92 ) 237 28 291 Cost of operations (85 ) 228 24 278 Total before tax 21 (58 ) (9 ) (71 ) Provision for Income Taxes $ (64 ) $ 170 $ 15 $ 207 Net Income Amortization of prior service cost on benefit obligations $ (488 ) $ (446 ) $ (993 ) $ (892 ) Other – net 25 157 208 313 Provision for Income Taxes $ (463 ) $ (289 ) $ (785 ) $ (579 ) Net Income Realized gain on investments $ — $ 126 $ — $ 148 Other – net — (6 ) — (14 ) Provision for Income Taxes $ — $ 120 $ — $ 134 Net Income Total reclassification for the period $ (527 ) $ 1 $ (770 ) $ (238 )
Schedule of Changes in Carrying Amount of Debt Issuance Costs	The following summarizes the changes in the carrying amount of our deferred debt issuance costs. Six Months Ended 2018 2017 (In thousands) Balance at beginning of period $ 4,202 $ 5,892 Additions 9,443 — Interest expense (1) (3,273 ) (850 ) Balance at end of period $ 10,372 $ 5,042 (1) Includes the recognition of prior deferred debt issuance costs associated with the Former Credit Facility of $2.4 million for the six months ended June 30, 2018 .
Restricted Cash and Cash Equivalents	The following table provides a reconciliation of cash and cash equivalents and restricted cash and cash equivalents within our condensed consolidated balance sheets to the totals presented in our condensed consolidated statement of cash flows: June 30, December 31, (In thousands) Cash and cash equivalents $ 317,624 $ 203,404 Restricted cash and cash equivalents 5,870 7,105 Restricted cash and cash equivalents included in Other Assets 2,647 2,635 Total cash and cash equivalents and restricted cash and cash equivalents as presented in our condensed consolidated statement of cash flows $ 326,141 $ 213,144
Restricted Cash and Cash Equivalents	The following table provides a reconciliation of cash and cash equivalents and restricted cash and cash equivalents within our condensed consolidated balance sheets to the totals presented in our condensed consolidated statement of cash flows: June 30, December 31, (In thousands) Cash and cash equivalents $ 317,624 $ 203,404 Restricted cash and cash equivalents 5,870 7,105 Restricted cash and cash equivalents included in Other Assets 2,647 2,635 Total cash and cash equivalents and restricted cash and cash equivalents as presented in our condensed consolidated statement of cash flows $ 326,141 $ 213,144
Summary of Changes in Carrying Amount of Accrued Warranty Expense	The following summarizes the changes in the carrying amount of our Accrued warranty expense: Six Months Ended 2018 2017 (In thousands) Balance at beginning of period $ 13,428 $ 11,477 Additions 810 667 Expirations and other changes (709 ) (84 ) Payments (347 ) (16 ) Translation (360 ) 173 Balance at end of period $ 12,822 $ 12,217

Revenue Recognition (Tables)

Revenue Recognition (Tables)	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Schedule of Initial Impact of the New Revenue Recognition Standard	A comparison of certain line items in our condensed consolidated statements of income is shown below: Three Months Ended Six Months Ended Current Method Historical Method Current Method Historical Method (In thousands) Revenues $ 438,921 $ 440,103 $ 896,384 $ 905,633 Cost of operations $ 318,209 $ 319,945 $ 645,573 $ 654,487 Operating Income $ 71,549 $ 70,995 $ 151,437 $ 151,772 Provision for Income Taxes $ 18,493 $ 18,311 $ 37,096 $ 37,043 Net Income $ 60,734 $ 60,362 $ 127,147 $ 127,535 The initial impact of the adoption of the FASB Topic Revenue from Contracts with Customers , which was recognized in a cumulative catch-up adjustment on January 1, 2018, is illustrated below: January 1, December 31, 2018 2017 (In thousands) Assets: Contracts in progress $ 260,932 $ 420,628 Deferred Income Taxes $ 85,193 $ 86,740 Liabilities: Accrued liabilities – other $ 66,371 $ 64,738 Advance billings on contracts $ 73,390 $ 246,192 Stockholders' Equity: Retained earnings $ 1,000,578 $ 990,652 A comparison of certain line items in our condensed consolidated balance sheet is shown below: June 30, 2018 Current Method Historical Method (In thousands) Assets: Contracts in progress $ 317,405 $ 348,762 Deferred Income Taxes $ 84,868 $ 85,295 Liabilities: Accrued liabilities – other $ 48,377 $ 45,572 Advance billings on contracts $ 77,775 $ 121,902 Stockholders' Equity: Retained earnings $ 1,097,665 $ 1,088,127
Schedule of Disaggregated Revenues	Revenues by geographical area and customer type are as follows: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Nuclear Nuclear Nuclear Total Nuclear Nuclear Nuclear Total (In thousands) United States: Government $ 327,896 $ 28,174 $ — $ 356,070 $ 644,527 $ 54,055 $ — $ 698,582 Non-Government 3,849 3,910 327 8,086 3,849 7,087 587 11,523 $ 331,745 $ 32,084 $ 327 $ 364,156 $ 648,376 $ 61,142 $ 587 $ 710,105 Canada: Government $ — $ — $ — $ — $ — $ — $ — $ — Non-Government — 510 64,743 65,253 — 1,485 147,068 148,553 $ — $ 510 $ 64,743 $ 65,253 $ — $ 1,485 $ 147,068 $ 148,553 Other: Government $ — $ — $ — $ — $ — $ — $ — $ — Non-Government 395 2 10,627 11,024 395 2 40,858 41,255 $ 395 $ 2 $ 10,627 $ 11,024 $ 395 $ 2 $ 40,858 $ 41,255 Segment Revenues $ 332,140 $ 32,596 $ 75,697 440,433 $ 648,771 $ 62,629 $ 188,513 899,913 Adjustments and Eliminations (1,512 ) (3,529 ) Revenues $ 438,921 $ 896,384 Revenues by timing of transfer of goods or services are as follows: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Nuclear Nuclear Nuclear Total Nuclear Nuclear Nuclear Total (In thousands) Over-time $ 332,140 $ 32,596 $ 69,324 $ 434,060 $ 648,771 $ 62,629 $ 174,433 $ 885,833 Point-in-time — — 6,373 6,373 — — 14,080 14,080 Segment Revenues $ 332,140 $ 32,596 $ 75,697 440,433 $ 648,771 $ 62,629 $ 188,513 899,913 Adjustments and Eliminations (1,512 ) (3,529 ) Revenues $ 438,921 $ 896,384 Revenues by contract type are as follows: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Nuclear Nuclear Nuclear Total Nuclear Nuclear Nuclear Total (In thousands) Fixed-Price Incentive Fee $ 258,150 $ — $ 5,589 $ 263,739 $ 507,390 $ — $ 9,617 $ 517,007 Firm-Fixed-Price 52,472 5,632 44,302 102,406 99,530 11,042 118,584 229,156 Cost-Plus Fee 21,450 26,086 — 47,536 41,683 50,039 45 91,767 Time-and-Materials 68 878 25,806 26,752 168 1,548 60,267 61,983 Segment Revenues $ 332,140 $ 32,596 $ 75,697 440,433 $ 648,771 $ 62,629 $ 188,513 899,913 Adjustments and Eliminations (1,512 ) (3,529 ) Revenues $ 438,921 $ 896,384
Schedule of Contract Assets and Liabilities	Our fixed-price incentive fee contracts for our Nuclear Operations Group segment include provisions that result in an increase in retainages on contracts during the first and third quarters of the year, with larger payments made during the second and fourth quarters. Retainages also vary as a result of timing differences between incurring costs and achieving milestones that allow us to recover these amounts. This resulted in an increase in retainages on contracts from January 1 to June 30, 2018 as shown below: June 30, January 1, 2018 2018 (In thousands) Included in Contracts in progress: Unbilled receivables $ 306,535 $ 250,325 Included in Accounts receivable – trade, net: Retainages $ 96,731 $ 82,801 Included in Other Assets: Retainages $ 1,626 $ 1,669 Advance billings on contracts $ 77,775 $ 73,390
Schedule of Remaining Performance Obligations	Of the June 30, 2018 remaining performance obligations on our contracts with customers, we expect to recognize revenues as follows: 2018 2019 Thereafter Total (In approximate millions) Nuclear Operations Group $ 630 $ 798 $ 1,258 $ 2,686 Nuclear Services Group 35 3 6 44 Nuclear Power Group 141 143 599 883 Total Remaining Performance Obligations $ 806 $ 944 $ 1,863 $ 3,613

Long-term Debt (Tables)

Long-term Debt (Tables)	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Schedule of Long-term Debt	Our Long-Term Debt consists of the following: June 30, December 31, (In thousands) Long-Term Debt: Senior Notes $ 400,000 $ — New Credit Facility 291,128 — Former Credit Facility — 513,131 Less: Amounts due within one year 14,556 27,870 Long-term debt, gross 676,572 485,261 Less: Deferred debt issuance costs 10,372 4,202 Long-term debt $ 666,200 $ 481,059

Pension Plans and Postretirem24

Pension Plans and Postretirement Benefits (Tables)	6 Months Ended
	Jun. 30, 2018
Defined Benefit Plan [Abstract]
Components of Net Periodic Benefit Cost	Components of net periodic benefit cost included in net income are as follows: Pension Benefits Other Benefits Three Months Ended Six Months Ended Three Months Ended Six Months Ended 2018 2017 2018 2017 2018 2017 2018 2017 (In thousands) Service cost $ 2,405 $ 2,145 $ 4,818 $ 4,296 $ 162 $ 153 $ 327 $ 307 Interest cost 12,307 13,495 24,650 27,008 351 538 900 1,078 Expected return on plan assets (21,553 ) (20,803 ) (43,178 ) (41,640 ) (399 ) (596 ) (1,033 ) (1,191 ) Amortization of prior service cost (credit) 550 525 1,100 1,050 (62 ) (78 ) (107 ) (157 ) Net periodic benefit (income) cost $ (6,291 ) $ (4,638 ) $ (12,610 ) $ (9,286 ) $ 52 $ 17 $ 87 $ 37

Derivative Financial Instrume25

Derivative Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Derivative Financial Instruments	The following tables summarize our derivative financial instruments at June 30, 2018 and December 31, 2017 : Asset and Liability Derivatives June 30, December 31, (In thousands) Derivatives Designated as Hedges: FX Forward Contracts: Location Accounts receivable – other $ 444 $ 250 Other Assets $ 468 $ 348 Accounts payable $ 219 $ 177 Other Liabilities $ 284 $ 93 Derivatives Not Designated as Hedges: FX Forward Contracts: Location Accounts receivable – other $ 5,000 $ —
Schedule of Effect of Derivative Instruments on Financial Statements	The effects of derivatives on our financial statements are outlined below: Three Months Ended Six Months Ended 2018 2017 2018 2017 (In thousands) Derivatives Designated as Hedges: Cash Flow Hedges: FX Forward Contracts: Amount of gain recognized in other comprehensive income $ (157 ) $ 551 $ 75 $ 927 Gain (loss) reclassified from accumulated other comprehensive income (loss) into earnings: effective portion Location Revenues $ 7 $ (9 ) $ (4 ) $ (13 ) Cost of operations $ (92 ) $ 237 $ 28 $ 291 Derivatives Not Designated as Hedges: FX Forward Contracts: Gain (loss) recognized in income Location Other – net $ 5,997 $ — $ 5,997 $ —

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Summary of Investments Measured at Fair Value	The following is a summary of our investments measured at fair value at June 30, 2018 : Total Level 1 Level 2 Level 3 (In thousands) Equity securities Equities $ 2,366 $ — $ 2,366 $ — Mutual funds 4,933 — 4,933 — Available-for-sale securities U.S. Government and agency securities 1,824 1,824 — — Corporate bonds 1,493 1,493 — — Asset-backed securities and collateralized mortgage obligations 140 — 140 — Total $ 10,756 $ 3,317 $ 7,439 $ — The following is a summary of our investments measured at fair value at December 31, 2017 : Total Level 1 Level 2 Level 3 (In thousands) Available-for-sale securities U.S. Government and agency securities $ 1,299 $ 1,299 $ — $ — Corporate bonds 3,169 1,534 1,635 — Equities 2,759 — 2,759 — Mutual funds 4,847 — 4,847 — Asset-backed securities and collateralized mortgage obligations 161 — 161 — Total $ 12,235 $ 2,833 $ 9,402 $ —

Segment Reporting (Tables)

Segment Reporting (Tables)	6 Months Ended
	Jun. 30, 2018
Segment Reporting [Abstract]
Schedule of Operating Results by Segment	An analysis of our operations by reportable segment is as follows: Three Months Ended Six Months Ended 2018 2017 2018 2017 (In thousands) REVENUES: Nuclear Operations Group $ 332,140 $ 312,866 $ 648,771 $ 637,947 Nuclear Services Group 32,596 44,785 62,629 72,639 Nuclear Power Group 75,697 54,569 188,513 132,243 Adjustments and Eliminations (1) (1,512 ) (2,209 ) (3,529 ) (4,589 ) $ 438,921 $ 410,011 $ 896,384 $ 838,240 (1) Segment revenues are net of the following intersegment transfers and other adjustments: Nuclear Operations Group Transfers $ (841 ) $ (205 ) $ (1,980 ) $ (400 ) Nuclear Services Group Transfers (702 ) (1,913 ) (1,540 ) (4,070 ) Nuclear Power Group Transfers 31 (91 ) (9 ) (119 ) $ (1,512 ) $ (2,209 ) $ (3,529 ) $ (4,589 ) OPERATING INCOME: Nuclear Operations Group $ 67,046 $ 69,295 $ 134,703 $ 137,044 Nuclear Services Group 3,511 15,399 4,688 15,801 Nuclear Power Group 7,810 5,712 29,574 18,668 Other (4,357 ) (1,070 ) (8,400 ) (2,682 ) $ 74,010 $ 89,336 $ 160,565 $ 168,831 Unallocated Corporate (2) (2,461 ) (3,908 ) (9,128 ) (7,131 ) Total Operating Income $ 71,549 $ 85,428 $ 151,437 $ 161,700 Other Income (Expense) : Interest income 441 211 1,219 348 Interest expense (7,869 ) (3,906 ) (11,429 ) (7,423 ) Other – net 15,106 6,749 23,016 14,235 Total Other Income (Expense) 7,678 3,054 12,806 7,160 Income before Provision for Income Taxes $ 79,227 $ 88,482 $ 164,243 $ 168,860 (2) Unallocated corporate includes general corporate overhead not allocated to segments.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings Per Share	The following table sets forth the computation of basic and diluted earnings per share: Three Months Ended Six Months Ended 2018 2017 2018 2017 (In thousands, except share and per share amounts) Basic: Net Income Attributable to BWX Technologies, Inc. $ 60,663 $ 61,263 $ 127,104 $ 116,982 Weighted-average common shares 99,681,580 99,166,205 99,603,884 99,305,558 Basic earnings per common share $ 0.61 $ 0.62 $ 1.28 $ 1.18 Diluted: Net Income Attributable to BWX Technologies, Inc. $ 60,663 $ 61,263 $ 127,104 $ 116,982 Weighted-average common shares (basic) 99,681,580 99,166,205 99,603,884 99,305,558 Effect of dilutive securities: Stock options, restricted stock units and performance shares (1) 890,157 984,721 938,130 1,115,390 Adjusted weighted-average common shares 100,571,737 100,150,926 100,542,014 100,420,948 Diluted earnings per common share $ 0.60 $ 0.61 $ 1.26 $ 1.16 (1) At June 30, 2018 and 2017 , none of our shares were antidilutive.

Basis of Presentation and Sig29

Basis of Presentation and Significant Accounting Policies - Additional Information (Details) $ in Thousands	Apr. 17, 2018centerpersonnel	Mar. 02, 2016USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)componentsegment	Jun. 30, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Basis Of Presentation And Significant Accounting Policies [Line Items]
Number of reportable segments | segment					3
Number of components supplied to worldwide (more than) | component					1,300
Accumulated other comprehensive income			$ (1,248)		$ (1,248)		$ (9,454)
Total inventories			11,700		11,700		8,600
Restricted cash and cash equivalents			$ 8,500		$ 8,500
Effective tax rate			23.30%	30.60%	22.60%	30.60%
Effective income tax rate reconciliation, share-based compensation cost (benefit) amount			$ (200)	$ (2,600)	$ (2,400)	$ (4,900)
Gross unrecognized tax benefits			800		800
Increase in cash and cash equivalents and restricted cash and cash equivalents			326,141	$ 157,930	326,141	$ 157,930	213,144	$ 134,600
Accounting Standards Update 2016-01
Basis Of Presentation And Significant Accounting Policies [Line Items]
Accumulated other comprehensive income							$ 2,200
Cash Held for Future Decommissioning of Facilities
Basis Of Presentation And Significant Accounting Policies [Line Items]
Restricted cash and cash equivalents			2,600		2,600
Cash Held to Meet Reinsurance Reserve Requirements
Basis Of Presentation And Significant Accounting Policies [Line Items]
Restricted cash and cash equivalents			$ 5,900		$ 5,900
Unsuccessful Outcome of Framework Agreement
Basis Of Presentation And Significant Accounting Policies [Line Items]
Loss contingency as a result of the Framework Agreement		$ 30,000
Canada Revenue Agency
Basis Of Presentation And Significant Accounting Policies [Line Items]
Statutory tax rate for Canada operations					25.00%
Sotera Health LLC's Nordion Medical Isotope Business
Basis Of Presentation And Significant Accounting Policies [Line Items]
Number of personnel acquired | personnel	150
Number of businesses acquired | center	2

Basis of Presentation and Sig30

Basis of Presentation and Significant Accounting Policies - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Currency translation adjustments	$ 6,415	$ 13,148
Net unrealized gain on derivative financial instruments	384	353
Unrecognized prior service cost on benefit obligations	(5,452)	(6,237)
Net unrealized gain (loss) on available-for-sale investments	(99)	2,190
Accumulated other comprehensive income	$ 1,248	$ 9,454

Basis of Presentation and Sig31

Basis of Presentation and Significant Accounting Policies - Schedule of Amounts Reclassified from Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues	$ 438,921	$ 410,011	$ 896,384	$ 838,240
Cost of operations	(318,209)	(278,356)	(645,573)	(581,572)
Total before tax	79,227	88,482	164,243	168,860
Other – net	15,106	6,749	23,016	14,235
Provision for Income Taxes	(18,493)	(27,062)	(37,096)	(51,654)
Net Income	60,734	61,420	127,147	117,206
Accumulated Other Comprehensive Income (Loss) Component Recognized
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income	(527)	1	(770)	(238)
Accumulated Other Comprehensive Income (Loss) Component Recognized | Realized gain (loss) on derivative financial instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues	7	(9)	(4)	(13)
Cost of operations	(92)	237	28	291
Total before tax	(85)	228	24	278
Provision for Income Taxes	21	(58)	(9)	(71)
Net Income	(64)	170	15	207
Accumulated Other Comprehensive Income (Loss) Component Recognized | Amortization of prior service cost on benefit obligations
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of operations	(488)	(446)
Other – net			(993)	(892)
Provision for Income Taxes	25	157	208	313
Net Income	(463)	(289)	(785)	(579)
Accumulated Other Comprehensive Income (Loss) Component Recognized | Realized gain on investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other – net	0	126	0	148
Provision for Income Taxes	0	(6)	0	(14)
Net Income	$ 0	$ 120	$ 0	$ 134

Basis of Presentation and Sig32

Basis of Presentation and Significant Accounting Policies Basis of Presentation and Significant Accounting Policies - Changes in Deferred Debt Issuance Costs (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Deferred Finance Costs [Roll Forward]
Balance at beginning of period	$ 4,202	$ 5,892
Additions			$ 9,443	$ 0
Interest expense	(3,273)	(850)
Balance at end of period	10,372	5,042
Recognition of debt issuance costs from Former Credit Facility	$ 2,441	$ 0

Basis of Presentation and Sig33

Basis of Presentation and Significant Accounting Policies - Reconciliation of Cash and Cash Equivalents and Restricted Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 317,624	$ 203,404
Restricted cash and cash equivalents	5,870	7,105
Restricted cash and cash equivalents included in Other Assets	2,647	2,635
Total cash and cash equivalents and restricted cash and cash equivalents as presented in our condensed consolidated statement of cash flows	$ 326,141	$ 213,144	$ 157,930	$ 134,600

Basis of Presentation and Sig34

Basis of Presentation and Significant Accounting Policies - Summary of Changes in Carrying Amount of Accrued Warranty Expense (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Movement in Product Warranty Accrual [Roll Forward]
Balance at beginning of period	$ 13,428	$ 11,477
Additions	810	667
Expirations and other changes	(709)	(84)
Payments	(347)	(16)
Translation	(360)	173
Balance at end of period	$ 12,822	$ 12,217

Revenue Recognition - Initial I

Revenue Recognition - Initial Impact of New Revenue Recognition Standard (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets
Contracts in progress	$ 317,405		$ 420,628
Deferred Income Taxes	84,868		86,740
Liabilities
Accrued liabilities – other	48,377		64,738
Advance billings on contracts	77,775		246,192
Stockholders' Equity
Retained earnings	1,097,665		990,652
Accounting Standards Update 2014-09
Assets
Contracts in progress	317,405	$ 260,932
Deferred Income Taxes	84,868	85,193
Liabilities
Accrued liabilities – other	48,377	66,371
Advance billings on contracts	77,775	73,390
Stockholders' Equity
Retained earnings	1,097,665	$ 1,000,578
Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Assets
Contracts in progress	348,762		420,628
Deferred Income Taxes	85,295		86,740
Liabilities
Accrued liabilities – other	45,572		64,738
Advance billings on contracts	121,902		246,192
Stockholders' Equity
Retained earnings	$ 1,088,127		$ 990,652

Revenue Recognition - Disaggreg

Revenue Recognition - Disaggregated Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 440,433		$ 899,913
Revenues	438,921	$ 410,011	896,384	$ 838,240
Fixed-Price Incentive Fee
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	263,739		517,007
Firm-Fixed-Price
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	102,406		229,156
Cost-Plus Fee
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	47,536		91,767
Time-and-Materials
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	26,752		61,983
Over-time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	434,060		885,833
Point-in-time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	6,373		14,080
UNITED STATES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	364,156		710,105
UNITED STATES | Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	356,070		698,582
UNITED STATES | Non-Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	8,086		11,523
CANADA
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	65,253		148,553
CANADA | Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
CANADA | Non-Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	65,253		148,553
Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	11,024		41,255
Other | Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Other | Non-Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	11,024		41,255
Nuclear Operations Group
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	332,140		648,771
Nuclear Operations Group | Fixed-Price Incentive Fee
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	258,150		507,390
Nuclear Operations Group | Firm-Fixed-Price
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	52,472		99,530
Nuclear Operations Group | Cost-Plus Fee
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	21,450		41,683
Nuclear Operations Group | Time-and-Materials
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	68		168
Nuclear Operations Group | Over-time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	332,140		648,771
Nuclear Operations Group | Point-in-time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Nuclear Services Group
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	32,596		62,629
Nuclear Services Group | Fixed-Price Incentive Fee
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Nuclear Services Group | Firm-Fixed-Price
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	5,632		11,042
Nuclear Services Group | Cost-Plus Fee
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	26,086		50,039
Nuclear Services Group | Time-and-Materials
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	878		1,548
Nuclear Services Group | Over-time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	32,596		62,629
Nuclear Services Group | Point-in-time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Nuclear Power Group
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	75,697		188,513
Nuclear Power Group | Fixed-Price Incentive Fee
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	5,589		9,617
Nuclear Power Group | Firm-Fixed-Price
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	44,302		118,584
Nuclear Power Group | Cost-Plus Fee
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		45
Nuclear Power Group | Time-and-Materials
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	25,806		60,267
Nuclear Power Group | Over-time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	69,324		174,433
Nuclear Power Group | Point-in-time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	6,373		14,080
Operating Segments | Nuclear Operations Group
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	332,140		648,771
Revenues	332,140	312,866	648,771	637,947
Operating Segments | Nuclear Operations Group | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	331,745		648,376
Operating Segments | Nuclear Operations Group | UNITED STATES | Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	327,896		644,527
Operating Segments | Nuclear Operations Group | UNITED STATES | Non-Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	3,849		3,849
Operating Segments | Nuclear Operations Group | CANADA
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Nuclear Operations Group | CANADA | Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Nuclear Operations Group | CANADA | Non-Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Nuclear Operations Group | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	395		395
Operating Segments | Nuclear Operations Group | Other | Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Nuclear Operations Group | Other | Non-Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	395		395
Operating Segments | Nuclear Services Group
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	32,596		62,629
Operating Segments | Nuclear Services Group | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	32,084		61,142
Operating Segments | Nuclear Services Group | UNITED STATES | Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	28,174		54,055
Operating Segments | Nuclear Services Group | UNITED STATES | Non-Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	3,910		7,087
Operating Segments | Nuclear Services Group | CANADA
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	510		1,485
Operating Segments | Nuclear Services Group | CANADA | Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Nuclear Services Group | CANADA | Non-Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	510		1,485
Operating Segments | Nuclear Services Group | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2		2
Operating Segments | Nuclear Services Group | Other | Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Nuclear Services Group | Other | Non-Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2		2
Operating Segments | Nuclear Power Group
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	75,697		188,513
Operating Segments | Nuclear Power Group | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	327		587
Operating Segments | Nuclear Power Group | UNITED STATES | Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Nuclear Power Group | UNITED STATES | Non-Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	327		587
Operating Segments | Nuclear Power Group | CANADA
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	64,743		147,068
Operating Segments | Nuclear Power Group | CANADA | Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Nuclear Power Group | CANADA | Non-Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	64,743		147,068
Operating Segments | Nuclear Power Group | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	10,627		40,858
Operating Segments | Nuclear Power Group | Other | Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Operating Segments | Nuclear Power Group | Other | Non-Government
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	10,627		40,858
Adjustments and Eliminations
Disaggregation of Revenue [Line Items]
Revenues	(1,512)	(2,209)	(3,529)	(4,589)
Adjustments and Eliminations | Nuclear Operations Group
Disaggregation of Revenue [Line Items]
Revenues	$ (841)	$ (205)	$ (1,980)	$ (400)

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net favorable changes in estimate that resulted in an increase in revenue		$ 14,500
Contracts in progress increase		56,200
Revenue recognized from advance billings on contracts		44,700
Revenue from contract with customer	$ 440,433	899,913
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	$ 1,200	$ 9,200

Revenue Recognition - Contract

Revenue Recognition - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018
Contracts with Customers, Asset and Liability [Line Items]
Advance billings on contracts	$ 77,775	$ 73,390
Contracts in Progress
Contracts with Customers, Asset and Liability [Line Items]
Contract with customer, asset	306,535	250,325
Accounts Receivable
Contracts with Customers, Asset and Liability [Line Items]
Contract with customer, asset	96,731	82,801
Other Assets
Contracts with Customers, Asset and Liability [Line Items]
Contract with customer, asset	$ 1,626	$ 1,669

Revenue Recognition - Remaining

Revenue Recognition - Remaining Performance Obligations (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	$ 806
Remaining performance obligation, expected timing of satisfaction, period	9 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	$ 944
Remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	$ 1,863
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	3,613
Nuclear Operations Group | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	630
Nuclear Operations Group | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	798
Nuclear Operations Group | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	1,258
Nuclear Operations Group | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	2,686
Nuclear Services Group | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	35
Nuclear Services Group | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	3
Nuclear Services Group | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	6
Nuclear Services Group | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	44
Nuclear Power Group | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	141
Nuclear Power Group | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	143
Nuclear Power Group | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	599
Nuclear Power Group | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Remaining Performance Obligations	$ 883

Revenue Recognition - Historica

Revenue Recognition - Historical Method (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Assets
Contracts in progress	$ 317,405		$ 317,405			$ 420,628
Deferred Income Taxes	84,868		84,868			86,740
Liabilities
Accrued liabilities – other	48,377		48,377			64,738
Advance billings on contracts	77,775		77,775			246,192
Stockholders' Equity
Retained earnings	1,097,665		1,097,665			990,652
Revenues	438,921	$ 410,011	896,384	$ 838,240
Cost of operations	318,209	278,356	645,573	581,572
Operating Income	71,549	85,428	151,437	161,700
Provision for Income Taxes	18,493	27,062	37,096	51,654
Net Income	60,734	$ 61,420	127,147	$ 117,206
Accounting Standards Update 2014-09
Assets
Contracts in progress	317,405		317,405		$ 260,932
Deferred Income Taxes	84,868		84,868		85,193
Liabilities
Accrued liabilities – other	48,377		48,377		66,371
Advance billings on contracts	77,775		77,775		73,390
Stockholders' Equity
Retained earnings	1,097,665		1,097,665		$ 1,000,578
Revenues	438,921		896,384
Cost of operations	318,209		645,573
Operating Income	71,549		151,437
Provision for Income Taxes	18,493		37,096
Net Income	60,734		127,147
Calculated under Revenue Guidance in Effect before Topic 606 | Accounting Standards Update 2014-09
Assets
Contracts in progress	348,762		348,762			420,628
Deferred Income Taxes	85,295		85,295			86,740
Liabilities
Accrued liabilities – other	45,572		45,572			64,738
Advance billings on contracts	121,902		121,902			246,192
Stockholders' Equity
Retained earnings	1,088,127		1,088,127			$ 990,652
Revenues	440,103		905,633
Cost of operations	319,945		654,487
Operating Income	70,995		151,772
Provision for Income Taxes	18,311		37,043
Net Income	$ 60,362		$ 127,535

Long-term Debt - Components of

Long-term Debt - Components of Long-term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Less: Amounts due within one year	$ 14,556	$ 27,870
Long-term debt, gross	676,572	485,261
Less: Deferred debt issuance costs	10,372	4,202	$ 5,042	$ 5,892
Long-term debt	666,200	481,059
Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross, including current maturities	400,000	0
Credit Facility | New Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross, including current maturities	291,128	0
Credit Facility | Former Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross, including current maturities	$ 0	$ 513,131

Long-term Debt (Details)

Long-term Debt (Details)	May 24, 2018USD ($)	Jun. 30, 2018USD ($)	Sep. 02, 2016USD ($)	May 11, 2015USD ($)
Debt Instrument [Line Items]
Maturity of long-term debt - 2018		$ 7,300,000
Maturity of long-term debt - 2019		14,600,000
Maturity of long-term debt - 2020		14,600,000
Maturity of long-term debt - 2021		14,600,000
Maturity of long-term debt - 2022		14,600,000
Maturity of long-term debt - 2023		225,600,000
Maturity of long-term debt - Thereafter		$ 400,000,000
Debt instrument redemption price percentage of principal amount redeemed	105.375%
Maximum
Debt Instrument [Line Items]
Debt instrument redemption price percentage	100.00%
Minimum
Debt Instrument [Line Items]
Debt instrument redemption price percentage	40.00%
New Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 250,000,000
EBITDA percentage	65.00%
Maximum leverage ratio	2.50
Commitment fee percentage of unused capacity		0.175%
Remaining borrowing capacity		$ 428,500,000
Weighted-average interest rate on outstanding borrowings		3.09%
Senior Notes | Senior Notes Due 2026
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount	$ 400,000,000
Debt instrument, interest rate	5.375%
Secured Debt | New Credit Facility
Debt Instrument [Line Items]
Maximum leverage ratio	4
Maximum leverage ratio, future increase	4.5
Maximum interest coverage ratio	3
Base Rate Loans | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Base Rate Loans | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	0.25%
New Revolving Credit Facility | New Credit Facility
Debt Instrument [Line Items]
Borrowings outstanding		$ 0
New Revolving Credit Facility | New Credit Facility | Maximum
Debt Instrument [Line Items]
Commitment fee percentage of unused capacity	0.275%
New Revolving Credit Facility | New Credit Facility | Minimum
Debt Instrument [Line Items]
Commitment fee percentage of unused capacity	0.15%
New Revolving Credit Facility | Secured Debt | New Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 500,000,000
Revolving Credit Facility | Secured Debt | Amended Credit Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity				$ 400,000,000
New USD Term Loan | Secured Debt | New Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	50,000,000
New CAD Term Loan | Secured Debt | New Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 250,000,000
Quarterly amortization payment, percentage of principal	1.25%
Term Loan Credit Facility | New Credit Facility
Debt Instrument [Line Items]
Borrowings outstanding		$ 291,100,000
Term Loan Credit Facility | Secured Debt | Amended Credit Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity				$ 300,000,000
Canadian Dollar Term Loan Facility | Secured Debt | Amended Credit Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 137,500,000
U.S. Dollar Term Loan Facility | Secured Debt | Amended Credit Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 112,500,000
Letter of Credit | New Credit Facility
Debt Instrument [Line Items]
Commitment fee percentage		1.375%
Borrowings outstanding		$ 71,500,000
Letter of Credit | New Credit Facility | Maximum
Debt Instrument [Line Items]
Commitment fee percentage of unused capacity	2.00%
Letter of Credit | New Credit Facility | Minimum
Debt Instrument [Line Items]
Commitment fee percentage of unused capacity	1.25%
Performance Letter Of Credit | New Credit Facility
Debt Instrument [Line Items]
Commitment fee percentage		0.825%
Performance Letter Of Credit | New Credit Facility | Maximum
Debt Instrument [Line Items]
Commitment fee percentage of unused capacity	1.20%
Performance Letter Of Credit | New Credit Facility | Minimum
Debt Instrument [Line Items]
Commitment fee percentage of unused capacity	0.75%
Eurodollar | New Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate		1.375%
Eurodollar | New Credit Facility | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	2.00%
Eurodollar | New Credit Facility | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.25%
Federal Funds Effective Swap Rate | New Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Thirty Day London Interbank Offered Rate LIBOR Plus | Base Rate Loans
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Base Rate | New Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate		0.375%

Pension Plans and Postretirem43

Pension Plans and Postretirement Benefits - (Details) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2018USD ($)retiree	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 2,600	$ 2,300	$ 5,100	$ 4,600
Net periodic benefit (income) cost, excluding service costs		(8,800)	(6,900)	(17,700)	(13,900)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 2,405	$ 2,145	$ 4,818	$ 4,296
Subsequent Event
Defined Benefit Plan Disclosure [Line Items]
Number of retirees transferred to annuity contract | retiree	1,300
Subsequent Event | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Transfer of domestic pension benefit obligation to annuity contract	$ 240,000

Pension Plans and Postretirem44

Pension Plans and Postretirement Benefits - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,600	$ 2,300	$ 5,100	$ 4,600
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2,405	2,145	4,818	4,296
Interest cost	12,307	13,495	24,650	27,008
Expected return on plan assets	(21,553)	(20,803)	(43,178)	(41,640)
Amortization of prior service cost (credit)	550	525	1,100	1,050
Net periodic benefit (income) cost	(6,291)	(4,638)	(12,610)	(9,286)
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	162	153	327	307
Interest cost	351	538	900	1,078
Expected return on plan assets	(399)	(596)	(1,033)	(1,191)
Amortization of prior service cost (credit)	(62)	(78)	(107)	(157)
Net periodic benefit (income) cost	$ 52	$ 17	$ 87	$ 37

Derivative Financial Instrume45

Derivative Financial Instruments - Additional Information (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net losses on derivative financial instruments in accumulated other comprehensive income	$ 0.4
Notional amount of foreign currency forward contracts	$ 249.4

Derivative Financial Instrume46

Derivative Financial Instruments - Summary of Derivative Financial Instruments (Details) - FX Forward Contracts - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Derivatives Designated as Hedges | Accounts receivable – other
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 444	$ 250
Derivatives Designated as Hedges | Other Assets
Derivatives, Fair Value [Line Items]
Asset Derivatives	468	348
Derivatives Designated as Hedges | Accounts payable
Derivatives, Fair Value [Line Items]
Liability Derivatives	219	177
Derivatives Designated as Hedges | Other Liabilities
Derivatives, Fair Value [Line Items]
Liability Derivatives	284	93
Derivatives Not Designated as Hedges | Accounts receivable – other
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 5,000	$ 0

Derivative Financial Instrume47

Derivative Financial Instruments - Schedule of Effect of Derivative Instruments on Statements of Financial Performance (Details) - Cash Flow Hedges - FX Forward Contracts - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivatives Designated as Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain recognized in other comprehensive income	$ (157)	$ 551	$ 75	$ 927
Derivatives Designated as Hedges | Revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) reclassified from accumulated other comprehensive income (loss) into earnings: effective portion	7	(9)	(4)	(13)
Derivatives Designated as Hedges | Cost of operations
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) reclassified from accumulated other comprehensive income (loss) into earnings: effective portion	(92)	237	28	291
Derivatives Not Designated as Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain recognized in other comprehensive income	$ 5,997	$ 0	$ 5,997	$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Investments and Available-for-Sale Securities Measured at Fair Value (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 10,756
Available-for-sale securities		$ 12,235
Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	2,366
Available-for-sale securities		2,759
Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	4,933
Available-for-sale securities		4,847
U.S. Government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,824
Available-for-sale securities		1,299
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,493
Available-for-sale securities		3,169
Asset-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	140
Available-for-sale securities		161
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	3,317
Available-for-sale securities		2,833
Level 1 | Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0
Available-for-sale securities		0
Level 1 | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0
Available-for-sale securities		0
Level 1 | U.S. Government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,824
Available-for-sale securities		1,299
Level 1 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,493
Available-for-sale securities		1,534
Level 1 | Asset-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0
Available-for-sale securities		0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	7,439
Available-for-sale securities		9,402
Level 2 | Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	2,366
Available-for-sale securities		2,759
Level 2 | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	4,933
Available-for-sale securities		4,847
Level 2 | U.S. Government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0
Available-for-sale securities		0
Level 2 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0
Available-for-sale securities		1,635
Level 2 | Asset-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	140
Available-for-sale securities		161
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0
Available-for-sale securities		0
Level 3 | Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0
Available-for-sale securities		0
Level 3 | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0
Available-for-sale securities		0
Level 3 | U.S. Government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0
Available-for-sale securities		0
Level 3 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0
Available-for-sale securities		0
Level 3 | Asset-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 0
Available-for-sale securities		$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
FX Forward Contracts
Fair Values Of Financial Instruments [Line Items]
Fair value of foreign currency forward contracts	$ 5.4	$ 0.3

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock based compensation expense	$ 1.4	$ 4	$ 6.3	$ 8.7
Stock-based compensation, tax benefits	$ 0.3	$ 1.4	$ 1.2	$ 3

Segment Reporting - Additional

Segment Reporting - Additional Information (Details)	6 Months Ended
	Jun. 30, 2018segment
Segment Reporting, Disclosure of Entity's Reportable Segments [Abstract]
Number of reportable segments	3

Segment Reporting - Schedule of

Segment Reporting - Schedule of Operating Results by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting, Other Significant Reconciling Item [Line Items]
Revenues	$ 438,921	$ 410,011	$ 896,384	$ 838,240
Operating Income	71,549	85,428	151,437	161,700
Interest income	441	211	1,219	348
Interest expense	(7,869)	(3,906)	(11,429)	(7,423)
Other – net	15,106	6,749	23,016	14,235
Total Other Income (Expense)	7,678	3,054	12,806	7,160
Income before Provision for Income Taxes	79,227	88,482	164,243	168,860
Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Operating Income	74,010	89,336	160,565	168,831
Operating Segments | Nuclear Operations Group
Segment Reporting, Other Significant Reconciling Item [Line Items]
Revenues	332,140	312,866	648,771	637,947
Operating Income	67,046	69,295	134,703	137,044
Operating Segments | Nuclear Services Group
Segment Reporting, Other Significant Reconciling Item [Line Items]
Revenues	32,596	44,785	62,629	72,639
Operating Income	3,511	15,399	4,688	15,801
Operating Segments | Nuclear Power Group
Segment Reporting, Other Significant Reconciling Item [Line Items]
Revenues	75,697	54,569	188,513	132,243
Operating Income	7,810	5,712	29,574	18,668
Operating Segments | Other
Segment Reporting, Other Significant Reconciling Item [Line Items]
Operating Income	(4,357)	(1,070)	(8,400)	(2,682)
Adjustments and Eliminations
Segment Reporting, Other Significant Reconciling Item [Line Items]
Revenues	(1,512)	(2,209)	(3,529)	(4,589)
Adjustments and Eliminations | Nuclear Operations Group
Segment Reporting, Other Significant Reconciling Item [Line Items]
Revenues	(841)	(205)	(1,980)	(400)
Adjustments and Eliminations | Nuclear Services Group
Segment Reporting, Other Significant Reconciling Item [Line Items]
Revenues	(702)	(1,913)	(1,540)	(4,070)
Adjustments and Eliminations | Nuclear Power Group
Segment Reporting, Other Significant Reconciling Item [Line Items]
Revenues	31	(91)	(9)	(119)
Unallocated Corporate
Segment Reporting, Other Significant Reconciling Item [Line Items]
Operating Income	$ (2,461)	$ (3,908)	$ (9,128)	$ (7,131)

Earnings Per Share - Computatio

Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Basic
Net income attributable to BWX Technologies, Inc.	$ 60,663	$ 61,263	$ 127,104	$ 116,982
Weighted-average common shares (in shares)	99,681,580	99,166,205	99,603,884	99,305,558
Basic earnings per common share (in usd per share)	$ 0.61	$ 0.62	$ 1.28	$ 1.18
Diluted
Net income attributable to BWX Technologies, Inc.	$ 60,663	$ 61,263	$ 127,104	$ 116,982
Weighted-average common shares (in shares)	99,681,580	99,166,205	99,603,884	99,305,558
Effect of dilutive securities
Stock options, restricted stock units and performance shares (in shares)	890,157	984,721	938,130	1,115,390
Adjusted weighted-average common shares (in shares)	100,571,737	100,150,926	100,542,014	100,420,948
Diluted earnings per common share (in usd per share)	$ 0.60	$ 0.61	$ 1.26	$ 1.16