Northwest Pipe (NWPX) 10-Q 5 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Nov. 01, 2013
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'NWPX	'
Entity Registrant Name	'NORTHWEST PIPE CO	'
Entity Central Index Key	'0001001385	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	9,449,299

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$33	$46
Trade and other receivables, less allowance for doubtful accounts of $719 and $1,748	64,609	41,498
Costs and estimated earnings in excess of billings on uncompleted contracts	51,066	73,314
Inventories	109,945	113,545
Refundable income taxes	1,339	'
Deferred income taxes	5,277	5,177
Prepaid expenses and other	1,708	2,558
Total current assets	233,977	236,138
Property and equipment, net	162,616	152,545
Goodwill	20,478	20,478
Other assets	16,642	13,261
Total assets	433,713	422,422
Current liabilities:	'	'
Current portion of long-term debt	5,714	5,714
Current portion of capital lease obligations	4,420	3,295
Accounts payable	22,063	21,042
Accrued liabilities	11,878	23,424
Deferred revenue	7,866	8,793
Billings in excess of costs and estimated earnings on uncompleted contracts	4,005	6,478
Total current liabilities	55,946	68,746
Note payable to financial institution	59,951	47,533
Long-term debt, less current portion	2,071	6,357
Capital lease obligations, less current portion	6,248	9,179
Deferred income taxes	18,957	15,254
Pension and other long-term liabilities	13,301	15,921
Total liabilities	156,474	162,990
Commitments and contingencies (Note 6)	'	'
Stockholders' equity:	'	'
Preferred stock, $.01 par value, 10,000,000 shares authorized, none issued or outstanding	'	'
Common stock, $.01 par value, 15,000,000 shares authorized, 9,449,299 and 9,382,994 shares issued and outstanding	94	94
Additional paid-in-capital	113,667	112,230
Retained earnings	165,464	149,381
Accumulated other comprehensive loss	-1,986	-2,273
Total stockholders' equity	277,239	259,432
Total liabilities and stockholders' equity	$433,713	$422,422

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Statement Of Financial Position [Abstract]	'	'
Trade and other receivables, allowance for doubtful accounts	$719	$1,748
Preferred stock, par value	$0.01	$0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	'	'
Preferred stock, shares outstanding	'	'
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	15,000,000	15,000,000
Common stock, shares issued	9,449,299	9,382,994
Common stock, shares outstanding	9,449,299	9,382,994

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement [Abstract]	'	'	'	'
Net sales	$103,022	$115,099	$360,357	$388,315
Cost of sales	94,210	103,499	314,673	346,638
Gross profit	8,812	11,600	45,684	41,677
Selling, general and administrative expense	5,972	7,571	18,644	21,499
Operating income	2,840	4,029	27,040	20,178
Other expense	242	49	279	51
Interest income	-141	-35	-384	-122
Interest expense	977	1,305	2,982	4,471
Income before income taxes	1,762	2,710	24,163	15,778
Provision for (benefit from) income taxes	746	-686	8,080	4,044
Net income	$1,016	$3,396	$16,083	$11,734
Basic earnings per share	$0.11	$0.36	$1.70	$1.25
Diluted earnings per share	$0.11	$0.36	$1.69	$1.24
Shares used in per share calculations:	'	'	'	'
Basic	9,449	9,383	9,443	9,375
Diluted	9,517	9,499	9,498	9,458

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]	'	'	'	'
Net income	$1,016	$3,396	$16,083	$11,734
Other comprehensive income (loss), net of tax:	'	'	'	'
Pension liability adjustment, net of tax	65	59	194	254
Deferred gain (loss) on cash flow derivatives, net of tax	-62	-168	93	-185
Other comprehensive income (loss), net of tax	3	-109	287	69
Comprehensive income	$1,019	$3,287	$16,370	$11,803

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Cash Flows From Operating Activities:	'	'
Net income	$16,083	$11,734
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	10,131	11,666
Provision for doubtful accounts	-1,029	-429
Amortization of debt issuance costs	476	1,119
Loss on impairment	250	'
Deferred income taxes	3,603	572
Loss on disposal of property and equipment	16	455
Stock based compensation expense	2,167	2,199
Unrealized (gain) loss on foreign currency forward contracts	-193	353
Changes in operating assets and liabilities:	'	'
Trade and other receivables, net	-22,082	-657
Costs and estimated earnings in excess of billings on uncompleted contracts, net	19,775	-18,351
Inventories	3,901	-24,078
Refundable income taxes	-1,339	-4,982
Prepaid expenses and other assets	1,702	4,099
Accounts payable	2,566	4,562
Deferred revenue	-927	10,129
Accrued and other liabilities	-13,715	23,808
Net cash provided by operating activities	21,385	22,199
Cash Flows From Investing Activities:	'	'
Additions to property and equipment	-22,080	-11,277
Proceeds from the sale of property and equipment	1,695	1,054
Issuance of notes receivable	-5,700	-1,000
Other investing activities	-250	'
Net cash used in investing activities	-26,335	-11,223
Cash Flows From Financing Activities:	'	'
Proceeds from issuance of common stock	72	37
Tax withholdings related to net share settlements of restricted stock units and performance share awards	-802	-212
Payments on long-term debt	-4,286	-4,286
Borrowings under note payable to financial institution	138,971	109,300
Payments on note payable to financial institution	-126,553	-113,011
Payments on capital lease obligations	-2,465	-2,557
Payments of debt amendment costs	'	-401
Net cash provided by (used in) financing activities	4,937	-11,130
Change in cash and cash equivalents	-13	-154
Cash and cash equivalents, beginning of period	46	182
Cash and cash equivalents, end of period	33	28
Non-cash investing activity:	'	'
Escrow account related to capital lease financing	'	898
Accrued property and equipment purchases	1,233	1,284
Capital lease additions	'	$142

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Basis of Presentation	'
	1	Basis of Presentation
	The Condensed Consolidated Financial Statements include the accounts of Northwest Pipe Company (the “Company”) and its subsidiaries in which the Company exercises control as of the financial statement date. Intercompany accounts and transactions have been eliminated. Prior period deferred revenue, which was previously reflected within accrued liabilities, has been reclassified (separated) to its own line item within net cash provided by operating activities to conform to current period presentation in the Condensed Consolidated Statements of Cash Flows. This reclassification has no impact on cash flows from operations, income from operations, net income, or total liabilities.
	The accompanying unaudited Condensed Consolidated Financial Statements have been prepared in conformity with accounting principles generally accepted in the United States of America. The financial information as of December 31, 2012 is derived from the audited consolidated financial statements presented in the Company’s Annual Report on Form 10-K for the year ended December 31, 2012 (the “2012 Form 10-K”). Certain information or footnote disclosures normally included in consolidated financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). In the opinion of management, the accompanying Condensed Consolidated Financial Statements include all adjustments necessary (which are of a normal and recurring nature) for the fair statement of the results of the interim periods presented. The Condensed Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements and notes thereto together with management’s discussion and analysis of financial condition and results of operations contained in the Company’s 2012 Form 10-K.
	Operating results for the three and nine months ended September 30, 2013 are not necessarily indicative of the results that may be expected for the entire fiscal year ending December 31, 2013.

Recent_Accounting_and_Reportin

Recent Accounting and Reporting Developments	9 Months Ended
	Sep. 30, 2013
Accounting Changes And Error Corrections [Abstract]	'
Recent Accounting and Reporting Developments	'
	2	Recent Accounting and Reporting Developments
	In December 2011, the FASB issued ASU 2011-11 which requires companies to disclose information regarding offsetting and other arrangements for derivatives and other financial instruments. In January 2013, the FASB issued ASU 2013-01, which limited the scope of the balance sheet offsetting disclosures to derivatives, repurchase agreements, and securities lending transactions to the extent that they are (1) offset in the financial statements or (2) subject to an enforceable master netting arrangement or similar agreement. This guidance is effective for interim and annual periods beginning on or after January 1, 2013. The Company adopted this guidance on January 1, 2013 and has made the required additional disclosures.
	In February 2013, the FASB issued ASU 2013-02, which clarified the reclassification requirements of ASU 2011-05 which were previously delayed by the FASB in October 2011. Reclassification adjustments which are not reclassified from other comprehensive income to net income in their entirety may instead be parenthetically cross referenced to the related footnote on the face of the financial statements for additional information. This guidance is effective for interim and annual reporting periods beginning after December 15, 2012. The Company adopted this guidance on January 1, 2013 and has made the required additional disclosures.
	In July 2013, the FASB issued ASU 2013-10, which allowed for the use of the Fed Funds Effective Swap rate (or Overnight Index Swap Rate) as a benchmark interest rate for hedge accounting purposes and removes the restriction on using different benchmark rates for similar hedges. This guidance is effective prospectively for qualifying new or redesignated hedging relationships entered into on or after July 17, 2013. The adoption of this guidance will not have a significant impact on the Company’s consolidated financial position or results of operation.
	In July 2013, the FASB issued ASU 2013-11, which clarified guidance on the presentation of unrecognized tax benefits. The guidance requires that an unrecognized tax benefit, or portion of an unrecognized tax benefit, be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward when such items exist in the same taxing jurisdiction. This guidance is effective for interim and annual periods beginning after December 15, 2013, with early adoption permitted. The amendments should be applied prospectively to all unrecognized tax benefits that exist at the effective date, and retrospective application is permitted. The adoption of this guidance is not expected to have a significant impact on the Company’s consolidated financial position.

Inventories

Inventories	9 Months Ended
	Sep. 30, 2013
Inventory Disclosure [Abstract]	'
Inventories	'
	3	Inventories
	Inventories are stated at the lower of cost or market and consist of the following (in thousands):
			September 30,		December 31,
			2013		2012
	Short-term inventories:
	Raw materials		$	45,624	$	56,913
	Work-in-process			1,187		10,157
	Finished goods			60,014		43,374
	Supplies			3,120		3,101
				109,945		113,545
	Long-term inventories:
	Finished goods			1,306		1,608
	Total inventories		$	111,251	$	115,153
	Long-term inventories are recorded in other assets.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	4	Fair Value Measurements
	The Company records its financial assets and liabilities at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability, in the principal or most advantageous market for the asset or liability, in an orderly transaction between market participants at the measurement date.
	The authoritative guidance establishes a fair value hierarchy which prioritizes the inputs to valuation techniques used to measure fair value into three broad levels. These levels are: Level 1 (inputs are quoted prices in active markets for identical assets or liabilities); Level 2 (inputs are other than quoted prices that are observable, either directly or indirectly through corroboration with observable market data); and Level 3 (inputs are unobservable, with little or no market data that exists, such as internal financial forecasts). The Company is required to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value.
	The following table summarizes information regarding the Company’s financial assets and financial liabilities that are measured at fair value (in thousands):
	Description		Balance at			Level 1		Level 2			Level 3
			September 30,
			2013
	Financial Assets
	Deferred compensation plan assets		$	5,627		$	5,627	$	—		$	—
	Derivatives			32			—		32			—
	Total Assets		$	5,659		$	5,627	$	32		$	—
	Financial Liabilities
	Derivatives		$	(44	)	$	—	$	(44	)	$	—
	Description		Balance at			Level 1		Level 2			Level 3
			December 31,
			2012
	Financial Assets
	Escrow account		$	898		$	898	$	—		$	—
	Deferred compensation plan assets			5,280			5,280		—			—
	Total Assets		$	6,178		$	6,178	$	—		$	—
	Financial Liabilities
	Derivatives		$	(353	)	$	—	$	(353	)	$	—
	The deferred compensation plan assets consist of cash and several publicly traded stock and bond mutual funds, valued using quoted market prices in active markets classified as Level 1 within the fair value hierarchy. The Company’s derivatives consist of foreign currency cash flow hedges and are valued using various pricing models or discounted cash flow analyses that incorporate observable market parameters, such as interest rate yield curves and currency rates, and are classified as Level 2 within the valuation hierarchy. Derivative valuations incorporate credit risk adjustments that are necessary to reflect the probability of default by the counterparty or the Company. The escrow account at December 31, 2012 consisted of a money market mutual fund and was valued using quoted market prices in active markets classified as Level 1 within the fair value hierarchy.
	The net carrying amounts of cash and cash equivalents, trade and other receivables, accounts payable, accrued liabilities and note payable to financial institution approximate fair value due to the short-term nature of these instruments. The fair value of our debt is calculated using a coupon rate on borrowings with similar maturities, current remaining average life to maturity, borrower credit quality, and current market conditions, all of which are classified as Level 2 within the valuation hierarchy. The fair value of the Company’s long-term debt, including the current portion, was $7.5 million and the carrying value was $7.8 million at September 30, 2013, and $11.5 million with a carrying value of $12.1 million at December 31, 2012.
	Financial Assets Measured and Recorded at Fair Value on a Non-Recurring Basis
	We measure our financial assets, including loans receivable and non-marketable equity method investments, at fair value on a non-recurring basis when they are determined to be other-than-temporarily impaired. The fair value of these assets is determined using Level 3 unobservable inputs due to the absence of observable market inputs and the valuations requiring management judgment. During the three and nine months ended September 30, 2013, there were $0.3 million of impairment charges recorded on investments. There were no impairment charges taken during the three and nine months ended September 30, 2012.

Derivative_Instruments_and_Hed

Derivative Instruments and Hedging Activities	9 Months Ended
	Sep. 30, 2013
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'
Derivative Instruments and Hedging Activities	'
	5	Derivative Instruments and Hedging Activities
	The Company conducts business in various foreign countries, and, from time to time, settles transactions in foreign currencies. The Company has established a program that utilizes foreign currency forward contracts to offset the risk associated with the effects of certain foreign currency exposures, typically arising from sales contracts denominated in Canadian currency. These derivative contracts are consistent with the Company’s strategy for financial risk management. The Company uses cash flow hedge accounting treatment for qualifying foreign currency forward contracts. The Company initially reports any gain or loss on the effective portion of a cash flow hedge as a component of other comprehensive income and subsequently reclassifies any gain or loss to net sales when the hedged revenues are recorded. Instruments that do not qualify for cash flow hedge accounting treatment are re-measured at fair value on each balance sheet date and resulting gains and losses are recognized in net income. As of September 30, 2013 and December 31, 2012, the total notional amount of the derivative contracts not designated as hedges was $0.6 million (CAD$0.6 million) and $2.7 million (CAD$2.6 million), respectively. As of September 30, 2013 and December 31, 2012, the total notional amount of the derivative contracts designated as hedges was $5.6 million (CAD$5.8 million) and $12.4 million (CAD$12.3 million), respectively.
	For each derivative contract for which the Company seeks to obtain cash flow hedge accounting treatment, the Company formally documents all relationships between hedging instruments and hedged items, as well as its risk management objective and strategy for undertaking the hedge transaction, the nature of the risk being hedged, how the hedging instrument’s effectiveness in offsetting the hedged risk will be assessed prospectively and retrospectively, and a description of the method of measuring ineffectiveness. This process includes linking all derivatives to specific firm commitments or forecasted transactions and designating the derivatives as cash flow hedges. The Company also formally assesses, both at the hedge’s inception and on an ongoing basis, whether the derivative contracts that are used in hedging transactions are highly effective in offsetting changes in cash flows of hedged items. The effective portion of these hedged items is reflected in other comprehensive income. If it is determined that a derivative contract is not highly effective, or that it has ceased to be a highly effective hedge, the Company will be required to discontinue hedge accounting with respect to that derivative contract prospectively.
	The balance sheet location and the fair values of derivative instruments are (in thousands):
			September 30,				December 31,
	Foreign Currency Forward Contracts		2013				2012
	Assets
	Derivatives designated as hedging instruments
	Prepaid expenses and other		$	7			$	—
	Derivatives not designated as hedging instruments
	Prepaid expenses and other			25				—
	Total assets		$	32			$	—
	Liabilities
	Derivatives designated as hedging instruments
	Accrued liabilities		$	—			$	197
	Derivatives not designated as hedging instruments
	Accrued liabilities			44				156
	Total liabilities		$	44			$	353
	All of the Company’s foreign currency forward contracts are subject to an enforceable master netting arrangement. The Company presents its foreign currency forward contract assets and liabilities within the Statement of Financial Position at their gross fair values.
			(i)				(ii)				(iii) (i) - (ii)				(iv)						(v) =xA0;(iii) - (iv)
															Gross Amounts Not Offset in
															the Statement of Financial Position
			Gross Amount of				Gross Amount				Net Amount of				Financial				Cash Collateral		Net Amount
			Recognized Assets				Offset in the				Assets Presented				Instruments				Received
							Statement of				in the Statement of
							Financial Position				Financial Position
	Derivative Assets
	September 30, 2013		$	32			$	—			$	32			$	32			$	—	$	—
	December 31, 2012		$	—			$	—			$	—			$	—			$	—	$	—
			(i)				(ii)				(iii) =i) - (ii)				(iv)						(v) =xA0;(iii) - (iv)
															Gross Amounts Not Offset in
															the Statement of Financial Position
			Gross Amount of				Gross Amount				Net Amount of				Financial				Cash Collateral		Net Amount
			Recognized Liabilities				Offset in the				Liabilities Presented				Instruments				Received
							Statement of				in the Statement of
							Financial Position				Financial Position
	Derivative Liabilities
	September 30, 2013		$	44			$	—			$	44			$	44			$	—	$	—
	December 31, 2012		$	353			$	—			$	353			$	353			$	—	$	—
	The amounts of the gains and losses related to the Company’s derivative contracts designated as hedging instruments for the three and nine months ended September 30, 2013 and September 30, 2012 are (in thousands):
			Pretax Gain (Loss) Recognized in Comprehensive
			Income on Effective Portion of Derivative
			Three months ended								Nine months ended
			September 30,								September 30,
			2013				2012				2013				2012
	Derivatives in Cash Flow Hedging Relationships
	Foreign currency forward contracts		$	(32	)		$	(300	)		$	279			$	(352	)
					Pretax Gain (Loss) Recognized in Income on Effective
					Portion of Derivative as a Result of Reclassification from
					Accumulated Other Comprehensive Loss
					Three months ended								Nine months ended
					September 30,								September 30,
			Location		2013				2012				2013				2012
	Derivatives in Cash Flow Hedging Relationships
	Foreign currency forward contracts		Net sales		$	66			$	(27	)		$	131			$	(19	)
					Gain (Loss) on Ineffective Portion of Derivative and Amount
					Excluded from Effectiveness Testing Recognized in Income
					Three months ended								Nine months ended
					September 30,								September 30,
			Location		2013				2012				2013				2012
	Derivatives in Cash Flow Hedging Relationships
	Foreign currency forward contracts		Net sales		$	3			$	(44	)		$	(50	)		$	(138	)
	At September 30, 2013, there is $14,000 of unrealized pretax gain on outstanding derivatives accumulated in other comprehensive loss, all of which is expected to be reclassified to net sales within the next 12 months as a result of underlying hedged transactions also being recorded in net sales.
For both the three and nine months ended September 30, 2013, the gains and losses from our derivative contracts not designated as hedging instruments recognized in net sales were a loss of $0.1 million. For the three and nine months ended September 30, 2012, the losses from our derivative contracts not designated as hedging instruments recognized in net sales were a loss of $0.3 million and a loss of $0.4 million, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2013
Commitments And Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	6	Commitments and Contingencies
	Portland Harbor Superfund
	On December 1, 2000, a section of the lower Willamette River known as the Portland Harbor was included on the National Priorities List at the request of the United States Environmental Protection Agency (the “EPA”). While the Company’s Portland, Oregon manufacturing facility does not border the Willamette River, an outfall from the facility’s stormwater system drains into a neighboring property’s privately owned stormwater system and slip. Since the listing of the site, the Company was notified by the EPA and the Oregon Department of Environmental Quality (the “ODEQ”) of potential liability under the Comprehensive Environmental Response, Compensation and Liability Act (“CERCLA”). In 2008, the Company was asked to file information disclosure reports with the EPA (CERCLA 104 (e) information request). By agreement with the EPA, the ODEQ is responsible for overseeing remedial investigation and source control activities for all upland sites to investigate sources and prevent future contamination to the river. A remedial investigation and feasibility study (“RI/FS”) of the Portland Harbor has been directed by a group of potentially responsible parties known as the Lower Willamette Group (the “LWG”) under agreement with the EPA. The Company made a payment of $175,000 to the LWG in June 2007 as part of an interim settlement, and is under no obligation to make any further payment. The final draft RI was submitted to the EPA by the LWG in fall of 2011 and the draft FS was submitted by the LWG to the EPA in March 2012. As of the date of this filing, the final RI and the revised FS are scheduled to be submitted to the EPA in the Spring of 2014.
	In 2001, groundwater containing elevated volatile organic compounds (“VOCs”) was identified in one localized area of leased property adjacent to the Portland facility furthest from the river. Assessment work in 2002 and 2003 to further characterize the groundwater was consistent with the initial conclusion that the source of the VOCs is located off of Company-owned property. In February 2005, the Company entered into a Voluntary Agreement for Remedial Investigation and Source Control Measures (the “Agreement”) with the ODEQ. The Company is one of many Upland Source Control Sites working with the ODEQ on Source Control and is considered a “medium” priority site by the ODEQ. The Company performed remedial investigation (“RI”) work required under the Agreement and submitted a draft RI/Source Control Evaluation Report in December 2005. The conclusions of the report indicated that the VOCs found in the groundwater do not present an unacceptable risk to human or ecological receptors in the Willamette River. The report also indicated there is no evidence at this time showing a connection between detected VOCs in groundwater and Willamette River sediments. In 2009, the ODEQ requested that the Company revise its RI/Source Control Evaluation Report from 2005 to include more recent information from focused supplemental sampling at the Portland facility and more recent information that has become available related to nearby properties. The Company submitted the Expanded Risk Assessment for the VOCs in Groundwater in May 2012. In February 2013, the ODEQ requested the Company revise the presented information in the 2012 Expanded Risk Assessment for the VOCs in Groundwater a second time, for submittal with the Final RI/Source Control Evaluation report in the fourth quarter of 2013 or first half of 2014.
	Also, based on sampling associated with the Portland facility’s RI and on sampling and reporting required under the Portland, Oregon manufacturing facility’s National Pollutant Discharge Elimination System permit for storm water, the Company and the ODEQ have periodically detected low concentrations of polynuclear aromatic hydrocarbons (“PAHs”), polychlorinated biphenyls (“PCBs”), and trace amounts of zinc in storm water. Storm water from the Portland, Oregon manufacturing facility site is discharged into a communal storm water system that ultimately discharges into the neighboring property’s privately owned slip. The slip was historically used for shipbuilding and subsequently for ship breaking and metal recycling. Studies of the river sediments have revealed trace concentrations of PAHs, PCBs and zinc, along with other constituents which are common constituents in urban storm water discharges. To minimize the pollutants in its storm water, the Company painted a substantial part of the Portland facility’s roofs in 2009 and installed a storm water treatment system in 2012. Stormwater discharge has remained below storm water benchmark levels ever since.
	Under the ODEQ Agreement, the Company submitted a Final Supplemental Work Plan to evaluate and assess soil and storm water, and further assess groundwater risk, as requested by the ODEQ. The Company submitted a remediation plan related to soil contamination, which the ODEQ approved. The Company has completed the approved remediation plan in 2011 and 2012, which included the excavation of localized soil and paving pervious surfaces. A final report on storm water source control with the Final RI/Source Control Evaluation report will be submitted in the fourth quarter of 2013 or the first half of 2014.
	During the localized soil excavation in 2011, additional stained soil was discovered. At the request of the ODEQ, the Company developed an additional Work Plan to characterize the nature and extent of soil and/or groundwater impacts from the staining. The Company began implementing this Work Plan in the second quarter of 2012 and submitted sampling results to the ODEQ in the third quarter of 2012. Comments from the ODEQ were received in November 2012. In February 2013, the ODEQ clarified its comments from November 2012, and the Company has completed its second round of groundwater sampling for the Stained Soil Investigation Area. The results will be reported to ODEQ in the fourth quarter of 2013 or the first half of 2014.
	The Company anticipates having to spend less than $0.1 million for further Source Control work in 2013.
	Concurrent with the activities of the EPA and the ODEQ, the Portland Harbor Natural Resources Trustee Council (“Trustees”) sent some or all of the same parties, including the Company, a notice of intent to perform a Natural Resource Damage Assessment (“NRDA”) for the Portland Harbor Site to determine the nature and extent of natural resource damages under CERCLA section 107. The Trustees for the Portland Harbor Site consist of representatives from several Northwest Indian Tribes, three federal agencies and one state agency. The Trustees act independently of the EPA and the ODEQ. The Trustees have encouraged potentially responsible parties to voluntarily participate in the funding of their injury assessments and several of those parties have agreed to do so. In 2009, one of the Tribal Trustees (the Yakima Nation) resigned and has requested funding from the same parties to support its own assessment. The Company has not assumed any payment obligation or liability related to either request.
	At this time, the Company is unable to estimate an amount or an amount within a range of costs for its obligation with respect to the Portland Harbor matters, and no further adjustment to the Condensed Consolidated Financial Statements has been recorded as of September 30, 2013.
	All Sites
	We operate our facilities under numerous governmental permits and licenses relating to air emissions, storm water run-off, and other environmental matters. Our operations are also governed by many other laws and regulations, including those relating to workplace safety and worker health, principally the Occupational Safety and Health Act and regulations there under which, among other requirements, establish noise and dust standards. We believe we are in material compliance with our permits and licenses and these laws and regulations, and we do not believe that future compliance with such laws and regulations will have a material adverse effect on our financial position, results of operations or cash flows.
	From time to time, the Company is involved in litigation relating to claims arising out of its operations in the normal course of its business. The Company maintains insurance coverage against potential claims in amounts that are believed to be adequate. The Company believes that it is not presently a party to any other litigation, the outcome of which would have a material adverse effect on its business, financial condition, results of operations or cash flows.
	Guarantees
	The Company has entered into certain stand-by letters of credit that total $3.1 million at September 30, 2013. The stand-by letters of credit relate to workers’ compensation insurance and equipment financing.

Segment_Information

Segment Information	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]	'
Segment Information	'
	7	Segment Information
	The Company’s operations are organized in two reportable segments, the Water Transmission Group and the Tubular Products Group, which are based on the nature of the products and the manufacturing process. The Water Transmission Group manufactures large-diameter, high-pressure steel pipeline systems for use in water infrastructure applications, primarily related to drinking water systems. These products are also used for hydroelectric power systems, wastewater systems and other applications. In addition, the Water Transmission Group makes products for industrial plant piping systems and certain structural applications. The Tubular Products Group manufactures and markets smaller diameter, electric resistance welded steel pipe used in a wide range of applications, including energy, construction, agriculture and industrial systems. These two segments represent distinct business activities, which management evaluates based on segment gross profit and operating income. Transfers between segments in the periods presented were not material.
			Three months ended September 30,						Nine months ended September 30,
			2013			2012			2013			2012
			(in thousands)						(in thousands)
	Net sales:
	Water Transmission		$	46,835		$	63,487		$	183,596		$	180,968
	Tubular Products			56,187			51,612			176,761			207,347
	Total		$	103,022		$	115,099		$	360,357		$	388,315
	Gross profit:
	Water Transmission		$	7,932		$	9,681		$	39,927		$	27,529
	Tubular Products			880			1,919			5,757			14,148
	Total		$	8,812		$	11,600		$	45,684		$	41,677
	Operating income (loss):
	Water Transmission		$	6,306		$	6,969		$	34,838		$	21,123
	Tubular Products			93			1,134			3,644			11,981
	Corporate			(3,559	)		(4,074	)		(11,442	)		(12,926	)
	Total		$	2,840		$	4,029		$	27,040		$	20,178

Sharebased_Compensation

Share-based Compensation	9 Months Ended
	Sep. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Share-based Compensation	'
	8	Share-based Compensation
	The Company has one active stock incentive plan for employees and directors, the 2007 Stock Incentive Plan, which provides for awards of stock options to purchase shares of common stock, stock appreciation rights, restricted and unrestricted shares of common stock, restricted stock units (RSUs) and performance share awards (PSAs). In addition, the Company has one inactive stock option plan, the 1995 Stock Option Plan for Nonemployee Directors, under which previously granted options remain outstanding.
	The Company recognizes compensation cost as service is rendered based on the fair value of the awards. The following summarizes share-based compensation expense recorded (in thousands):
			Three months ended September 30,					Nine months ended September 30,
			2013			2012		2013		2012
	Cost of sales		$	199		$	145	$	466	$	287
	Selling, general and administrative expenses			678			780		1,701		1,912
	Total		$	877		$	925	$	2,167	$	2,199
	As of September 30, 2013, unrecognized compensation expense related to the unvested portion of the Company’s RSUs and PSAs was $4.9 million which is expected to be recognized over a weighted average period of 1.9 years.
	Stock Option Awards
	A summary of the status of the Company’s stock options as of September 30, 2013 and changes during the nine months then ended is presented below:
			Options			Weighted		Weighted		Aggregate
			Outstanding			Average		Average		Intrinsic Value
						Exercise Price		Remaining
						per Share		Contractual
								Life
										(In thousands)
	Balance, January 1, 2013			47,000		$	23.19
	Options granted			—			—
	Options exercised or exchanged			(7,000	)		10.31
	Options canceled			—			—
	Balance, September 30, 2013			40,000			25.44		4.9	$	309
	Exercisable, September 30, 2013			40,000			25.44		4.9	$	309
	The total intrinsic value, defined as the difference between the current market value and the grant price, of options exercised or exchanged during the nine months ended September 30, 2013 was $0.1 million.
	Restricted Stock Units and Performance Awards
	A summary of the status of the Company’s RSUs and PSAs as of September 30, 2013 and changes during the nine months then ended is presented below:
			Number of RSUs			Weighted Average
			and PSAs			Grant Date Fair Value
	Unvested RSUs and PSAs at January 1, 2013			243,141		$	26.11
	RSUs and PSAs granted			122,878			33.97
	RSUs and PSAs vested			(92,930	)		23.59
	RSUs and PSAs canceled			(13,521	)		26.86
	Unvested RSUs and PSAs at September 30, 2013			259,568			30.69
	RSUs and PSAs are measured at the estimated fair value on the date of grant. RSUs are service-based awards and vest according to vesting schedules, which range from immediate to ratably over a three-year period. PSAs are service-based awards with a market-based vesting condition. Vesting of the market-based PSAs is dependent upon the performance of the market price of the Company’s stock relative to a peer group of companies and ranges from two to three years. The unvested balance of RSUs and PSAs at September 30, 2013 includes approximately 198,000 PSAs at a target level of performance; the actual number of common shares that will ultimately be issued will be determined by multiplying this number of PSAs by a payout percentage ranging from 0% to 200%.
	Stock Awards
	For the nine months ended September 30, 2013 and 2012, stock awards of 4,912 and 4,807 shares, respectively, were granted to non-employee directors, which vested immediately upon issuance. The Company recorded compensation expense based on the fair market value per share of the awards on the grant date of $27.49 and $23.40 in 2013 and 2012, respectively.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	9	Income Taxes
	The Company files income tax returns in the United States Federal jurisdiction, in a limited number of foreign jurisdictions, and in many state jurisdictions. The Company is currently under examination by the Internal Revenue Service for years 2009, 2010 and 2011. With few exceptions, the Company is no longer subject to U.S. Federal, state or foreign income tax examinations for years before 2009.
	The Company had $5.6 million and $5.2 million of unrecognized tax benefits at September 30, 2013 and December 31, 2012, respectively. The Company believes it is reasonably possible that the total amounts of unrecognized tax benefits will change in the following twelve months; however, actual results could differ from those currently expected. Of the balance of unrecognized tax benefits, $2.2 million would affect the Company’s effective tax rate if recognized at some point in the future.
	The Company recognizes interest and penalties related to uncertain tax positions in income tax expense. The Company provided for income taxes at estimated effective tax rates of 42.3% and 33.4%, respectively, for the three and nine month periods ended September 30, 2013. The Company’s effective rate for the three months ended September 30, 2013 was greater than our federal statutory rate of 35% primarily due to an increase in the valuation allowance related to an investment in which the Company is anticipating a future capital loss. The Company’s effective tax rate was less than our federal statutory rate for the first nine months of 2013 primarily due to the favorable impact of the research and development tax credit. The Company provided for income taxes at an estimated effective tax benefit rate of 25.3% and an estimated effective tax rate of 26.5%, respectively, for the three and nine month periods ended September 30, 2012. During the third quarter of 2012, the Company performed a research and development tax credit study for fiscal years 2010 through 2011. The Company recorded a net tax benefit of $1.8 million resulting from this study in the third quarter of 2012. Combined with the operating results for the quarter, the Company’s effective rates for the three and nine months ended September 30, 2012 were therefore less than our federal statutory rate of 35%.

Earnings_per_Share

Earnings per Share	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]	'
Earnings per Share	'
	10	Earnings per Share
	Earnings per basic and diluted weighted average common share outstanding were calculated as follows for the three and nine months ended September 30, 2013 and 2012 (in thousands, except per share data):
			Three Months Ended September 30,				Nine Months Ended September 30,
			2013		2012		2013		2012
	Net income		$	1,016	$	3,396	$	16,083	$	11,734
	Basic weighted-average common shares outstanding			9,449		9,383		9,443		9,375
	Effect of potentially dilutive common shares(1)			68		116		55		83
	Diluted weighted-average common shares outstanding			9,517		9,499		9,498		9,458
	Earnings per common share:
	Earnings per basic common share		$	0.11	$	0.36	$	1.7	$	1.25
	Earnings per diluted common share		$	0.11	$	0.36	$	1.69	$	1.24
	Antidilutive shares not included in diluted common share calculation			93		96		97		120
	-1	Represents the effect of the assumed exercise of stock options and the vesting of restricted stock units and performance stock awards, based on the treasury stock method.

Changes_in_Accumulated_Other_C

Changes in Accumulated Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]	'
Changes in Accumulated Other Comprehensive Loss	'
	11	Changes in Accumulated Other Comprehensive Loss
	The following table summarizes changes in the components of accumulated other comprehensive income (loss) during the nine months ended September 30, 2013 (in thousands). All amounts are net of tax:
			Defined Benefit			Gains (Losses) on			Total
			Pension Items			Cash Flow
						Hedges
	Balance, December 31, 2012		$	(2,188	)	$	(85	)	$	(2,273	)
	Other comprehensive income before reclassifications			—			175			175
	Amounts reclassified from accumulated other comprehensive income (loss)			194			(82	)		112
	Net current period other comprehensive income			194			93			287
	Balance, September 30, 2013		$	(1,994	)	$	8		$	(1,986	)
	The following table provides additional detail about accumulated other comprehensive income (loss) components which were reclassified to the Condensed Consolidated Statement of Operations during the nine months ended September 30, 2013 (in thousands):
	Details about Accumulated Other		Amount reclassified from			Affected line item in the
	Comprehensive Income (Loss) Components		Accumulated Other			Condensed Consolidated
			Comprehensive Income (Loss)			Statement of Income
	Defined Benefit Pension Items
	Net periodic pension cost		$	(295	)	Cost of sales
				101		Tax benefit
			$	(194	)	Net of tax
	Gains and losses on cash flow hedges
	Foreign currency forward contracts		$	131		Net sales
				(49	)	Tax expense
			$	82		Net of tax
	Total reclassifications for the period		$	(112	)

Basis_of_Presentation_Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Consolidation Policy	'
	The Condensed Consolidated Financial Statements include the accounts of Northwest Pipe Company (the “Company”) and its subsidiaries in which the Company exercises control as of the financial statement date. Intercompany accounts and transactions have been eliminated.
Basis of Accounting	'
	The accompanying unaudited Condensed Consolidated Financial Statements have been prepared in conformity with accounting principles generally accepted in the United States of America. The financial information as of December 31, 2012 is derived from the audited consolidated financial statements presented in the Company’s Annual Report on Form 10-K for the year ended December 31, 2012 (the “2012 Form 10-K”). Certain information or footnote disclosures normally included in consolidated financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). In the opinion of management, the accompanying Condensed Consolidated Financial Statements include all adjustments necessary (which are of a normal and recurring nature) for the fair statement of the results of the interim periods presented. The Condensed Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements and notes thereto together with management’s discussion and analysis of financial condition and results of operations contained in the Company’s 2012 Form 10-K.

Inventories_Tables

Inventories (Tables)	9 Months Ended
	Sep. 30, 2013
Inventory Disclosure [Abstract]	'
Components of Inventories	'
	Inventories are stated at the lower of cost or market and consist of the following (in thousands):
		September 30,		December 31,
		2013		2012
	Short-term inventories:
	Raw materials	$	45,624	$	56,913
	Work-in-process		1,187		10,157
	Finished goods		60,014		43,374
	Supplies		3,120		3,101
			109,945		113,545
	Long-term inventories:
	Finished goods		1,306		1,608
	Total inventories	$	111,251	$	115,153

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Assets and Liabilities Measured at Fair Value on a Recurring Basis	'
	The following table summarizes information regarding the Company’s financial assets and financial liabilities that are measured at fair value (in thousands):
	Description	Balance at			Level 1		Level 2			Level 3
		September 30,
		2013
	Financial Assets
	Deferred compensation plan assets	$	5,627		$	5,627	$	—		$	—
	Derivatives		32			—		32			—
	Total Assets	$	5,659		$	5,627	$	32		$	—
	Financial Liabilities
	Derivatives	$	(44	)	$	—	$	(44	)	$	—
	Description	Balance at			Level 1		Level 2			Level 3
		December 31,
		2012
	Financial Assets
	Escrow account	$	898		$	898	$	—		$	—
	Deferred compensation plan assets		5,280			5,280		—			—
	Total Assets	$	6,178		$	6,178	$	—		$	—
	Financial Liabilities
	Derivatives	$	(353	)	$	—	$	(353	)	$	—

Derivative_Instruments_and_Hed1

Derivative Instruments and Hedging Activities (Tables)	9 Months Ended
	Sep. 30, 2013
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'
Balance Sheet Location and Fair Values of Derivative Instruments	'
	The balance sheet location and the fair values of derivative instruments are (in thousands):
		September 30,				December 31,
	Foreign Currency Forward Contracts	2013				2012
	Assets
	Derivatives designated as hedging instruments
	Prepaid expenses and other	$	7			$	—
	Derivatives not designated as hedging instruments
	Prepaid expenses and other		25				—
	Total assets	$	32			$	—
	Liabilities
	Derivatives designated as hedging instruments
	Accrued liabilities	$	—			$	197
	Derivatives not designated as hedging instruments
	Accrued liabilities		44				156
	Total liabilities	$	44			$	353
Balance Sheet Offsetting Disclosure	'
	The Company presents its foreign currency forward contract assets and liabilities within the Statement of Financial Position at their gross fair values.
		(i)				(ii)				(iii) (i) - (ii)				(iv)						(v) =xA0;(iii) - (iv)
														Gross Amounts Not Offset in
														the Statement of Financial Position
		Gross Amount of				Gross Amount				Net Amount of				Financial				Cash Collateral		Net Amount
		Recognized Assets				Offset in the				Assets Presented				Instruments				Received
						Statement of				in the Statement of
						Financial Position				Financial Position
	Derivative Assets
	September 30, 2013	$	32			$	—			$	32			$	32			$	—	$	—
	December 31, 2012	$	—			$	—			$	—			$	—			$	—	$	—
		(i)				(ii)				(iii) =i) - (ii)				(iv)						(v) =xA0;(iii) - (iv)
														Gross Amounts Not Offset in
														the Statement of Financial Position
		Gross Amount of				Gross Amount				Net Amount of				Financial				Cash Collateral		Net Amount
		Recognized Liabilities				Offset in the				Liabilities Presented				Instruments				Received
						Statement of				in the Statement of
						Financial Position				Financial Position
	Derivative Liabilities
	September 30, 2013	$	44			$	—			$	44			$	44			$	—	$	—
	December 31, 2012	$	353			$	—			$	353			$	353			$	—	$	—
Gains and Losses Related to Derivative Contracts Designated as Hedging Instruments	'
	The amounts of the gains and losses related to the Company’s derivative contracts designated as hedging instruments for the three and nine months ended September 30, 2013 and September 30, 2012 are (in thousands):
		Pretax Gain (Loss) Recognized in Comprehensive
		Income on Effective Portion of Derivative
		Three months ended								Nine months ended
		September 30,								September 30,
		2013				2012				2013				2012
	Derivatives in Cash Flow Hedging Relationships
	Foreign currency forward contracts	$	(32	)		$	(300	)		$	279			$	(352	)
				Pretax Gain (Loss) Recognized in Income on Effective
				Portion of Derivative as a Result of Reclassification from
				Accumulated Other Comprehensive Loss
				Three months ended								Nine months ended
				September 30,								September 30,
		Location		2013				2012				2013				2012
	Derivatives in Cash Flow Hedging Relationships
	Foreign currency forward contracts	Net sales		$	66			$	(27	)		$	131			$	(19	)
				Gain (Loss) on Ineffective Portion of Derivative and Amount
				Excluded from Effectiveness Testing Recognized in Income
				Three months ended								Nine months ended
				September 30,								September 30,
		Location		2013				2012				2013				2012
	Derivatives in Cash Flow Hedging Relationships
	Foreign currency forward contracts	Net sales		$	3			$	(44	)		$	(50	)		$	(138	)

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]	'
Segment Information Report of Statements of Operations	'
	Transfers between segments in the periods presented were not material.
		Three months ended September 30,						Nine months ended September 30,
		2013			2012			2013			2012
		(in thousands)						(in thousands)
	Net sales:
	Water Transmission	$	46,835		$	63,487		$	183,596		$	180,968
	Tubular Products		56,187			51,612			176,761			207,347
	Total	$	103,022		$	115,099		$	360,357		$	388,315
	Gross profit:
	Water Transmission	$	7,932		$	9,681		$	39,927		$	27,529
	Tubular Products		880			1,919			5,757			14,148
	Total	$	8,812		$	11,600		$	45,684		$	41,677
	Operating income (loss):
	Water Transmission	$	6,306		$	6,969		$	34,838		$	21,123
	Tubular Products		93			1,134			3,644			11,981
	Corporate		(3,559	)		(4,074	)		(11,442	)		(12,926	)
	Total	$	2,840		$	4,029		$	27,040		$	20,178

Sharebased_Compensation_Tables

Share-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Summary of Share-Based Compensation Expense	'
	The Company recognizes compensation cost as service is rendered based on the fair value of the awards. The following summarizes share-based compensation expense recorded (in thousands):
		Three months ended September 30,					Nine months ended September 30,
		2013			2012		2013		2012
	Cost of sales	$	199		$	145	$	466	$	287
	Selling, general and administrative expenses		678			780		1,701		1,912
	Total	$	877		$	925	$	2,167	$	2,199
Schedule of Share-Based Compensation, Stock Options, Activity	'
	A summary of the status of the Company’s stock options as of September 30, 2013 and changes during the nine months then ended is presented below:
		Options			Weighted		Weighted		Aggregate
		Outstanding			Average		Average		Intrinsic Value
					Exercise Price		Remaining
					per Share		Contractual
							Life
									(In thousands)
	Balance, January 1, 2013		47,000		$	23.19
	Options granted		—			—
	Options exercised or exchanged		(7,000	)		10.31
	Options canceled		—			—
	Balance, September 30, 2013		40,000			25.44		4.9	$	309
	Exercisable, September 30, 2013		40,000			25.44		4.9	$	309
Summary of the Status of the Company's RSUs and PSAs	'
	A summary of the status of the Company’s RSUs and PSAs as of September 30, 2013 and changes during the nine months then ended is presented below:
		Number of RSUs			Weighted Average
		and PSAs			Grant Date Fair Value
	Unvested RSUs and PSAs at January 1, 2013		243,141		$	26.11
	RSUs and PSAs granted		122,878			33.97
	RSUs and PSAs vested		(92,930	)		23.59
	RSUs and PSAs canceled		(13,521	)		26.86
	Unvested RSUs and PSAs at September 30, 2013		259,568			30.69

Earnings_per_Share_Tables

Earnings per Share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]	'
Earnings per Basic and Diluted Weighted Average Common Share Outstanding	'
	Earnings per basic and diluted weighted average common share outstanding were calculated as follows for the three and nine months ended September 30, 2013 and 2012 (in thousands, except per share data):
			Three Months Ended September 30,				Nine Months Ended September 30,
			2013		2012		2013		2012
	Net income		$	1,016	$	3,396	$	16,083	$	11,734
	Basic weighted-average common shares outstanding			9,449		9,383		9,443		9,375
	Effect of potentially dilutive common shares(1)			68		116		55		83
	Diluted weighted-average common shares outstanding			9,517		9,499		9,498		9,458
	Earnings per common share:
	Earnings per basic common share		$	0.11	$	0.36	$	1.7	$	1.25
	Earnings per diluted common share		$	0.11	$	0.36	$	1.69	$	1.24
	Antidilutive shares not included in diluted common share calculation			93		96		97		120
	-1	Represents the effect of the assumed exercise of stock options and the vesting of restricted stock units and performance stock awards, based on the treasury stock method.

Changes_in_Accumulated_Other_C1

Changes in Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]	'
Schedule of Accumulated Other Comprehensive Income (Loss)	'
	The following table summarizes changes in the components of accumulated other comprehensive income (loss) during the nine months ended September 30, 2013 (in thousands). All amounts are net of tax:
		Defined Benefit			Gains (Losses) on			Total
		Pension Items			Cash Flow
					Hedges
	Balance, December 31, 2012	$	(2,188	)	$	(85	)	$	(2,273	)
	Other comprehensive income before reclassifications		—			175			175
	Amounts reclassified from accumulated other comprehensive income (loss)		194			(82	)		112
	Net current period other comprehensive income		194			93			287
	Balance, September 30, 2013	$	(1,994	)	$	8		$	(1,986	)
Schedule of Effect on Net Income of Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	'
	The following table provides additional detail about accumulated other comprehensive income (loss) components which were reclassified to the Condensed Consolidated Statement of Operations during the nine months ended September 30, 2013 (in thousands):
	Details about Accumulated Other	Amount reclassified from			Affected line item in the
	Comprehensive Income (Loss) Components	Accumulated Other			Condensed Consolidated
		Comprehensive Income (Loss)			Statement of Income
	Defined Benefit Pension Items
	Net periodic pension cost	$	(295	)	Cost of sales
			101		Tax benefit
		$	(194	)	Net of tax
	Gains and losses on cash flow hedges
	Foreign currency forward contracts	$	131		Net sales
			(49	)	Tax expense
		$	82		Net of tax
	Total reclassifications for the period	$	(112	)

Inventories_Components_of_Inve

Inventories - Components of Inventories (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Short-term inventories:	'	'
Raw materials	$45,624	$56,913
Work-in-process	1,187	10,157
Finished goods	60,014	43,374
Supplies	3,120	3,101
Total short-term inventories	109,945	113,545
Long-term inventories:	'	'
Finished goods	1,306	1,608
Total inventories	$111,251	$115,153

Fair_Value_Measurements_Assets

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Financial Assets	'	'
Derivatives	$32	'
Financial Liabilities	'	'
Derivatives	-44	-353
Recurring [Member]	'	'
Financial Assets	'	'
Escrow account	'	898
Deferred compensation plan assets	5,627	5,280
Derivatives	32	'
Total Assets	5,659	6,178
Financial Liabilities	'	'
Derivatives	-44	-353
Level 1 [Member] | Recurring [Member]	'	'
Financial Assets	'	'
Escrow account	'	898
Deferred compensation plan assets	5,627	5,280
Derivatives	'	'
Total Assets	5,627	6,178
Financial Liabilities	'	'
Derivatives	'	'
Level 2 [Member] | Recurring [Member]	'	'
Financial Assets	'	'
Escrow account	'	'
Deferred compensation plan assets	'	'
Derivatives	32	'
Total Assets	32	'
Financial Liabilities	'	'
Derivatives	-44	-353
Level 3 [Member] | Recurring [Member]	'	'
Financial Assets	'	'
Escrow account	'	'
Deferred compensation plan assets	'	'
Derivatives	'	'
Total Assets	'	'
Financial Liabilities	'	'
Derivatives	'	'

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Fair Value Disclosures [Abstract]	'	'	'	'	'
Fair value of long-term debt	$7.50	'	$7.50	'	$11.50
Carrying value of long-term debt	7.8	'	7.8	'	12.1
Non-recurring fair value measurement impairment charge	$0.30	$0	$0.30	$0	'

Derivative_Instruments_and_Hed2

Derivative Instruments and Hedging Activities - Additional Information (Detail)

3 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Dec. 31, 2012

USD ($)

USD ($)

USD ($)

USD ($)

Not designated as hedging instrument [Member]

Not designated as hedging instrument [Member]

Not designated as hedging instrument [Member]

Not designated as hedging instrument [Member]

Designated as hedging instrument [Member]

Designated as hedging instrument [Member]

Designated as hedging instrument [Member]

Designated as hedging instrument [Member]

USD ($)

CAD

USD ($)

CAD

USD ($)

CAD

USD ($)

CAD

Derivatives, Fair Value [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Notional amount of Canadian forward contracts

'

'

'

'

$600,000

600,000

$2,700,000

2,600,000

$5,600,000

5,800,000

$12,400,000

12,300,000

Unrealized pretax gain on outstanding derivatives accumulated in other comprehensive loss expected to be reclassified within 12 months

14,000

'

14,000

'

'

'

'

'

'

'

'

'

Gain (loss) from derivative contracts not designated as hedging instruments recognized in net sales

($100,000)

($300,000)

($100,000)

($400,000)

'

'

'

'

'

'

'

'

Derivative_Instruments_and_Hed3

Derivative Instruments and Hedging Activities - Balance Sheet Location and Fair Values of Derivative Instruments (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Assets	'	'
Total assets	$32	'
Liabilities	'	'
Total liabilities	44	353
Designated as hedging instrument [Member] | Prepaid expenses and other [Member]	'	'
Assets	'	'
Derivative assets	7	'
Designated as hedging instrument [Member] | Accrued liabilities [Member]	'	'
Liabilities	'	'
Derivative Liabilities	'	197
Not designated as hedging instrument [Member] | Prepaid expenses and other [Member]	'	'
Assets	'	'
Derivative assets	25	'
Not designated as hedging instrument [Member] | Accrued liabilities [Member]	'	'
Liabilities	'	'
Derivative Liabilities	$44	$156

Derivative_Instruments_and_Hed4

Derivative Instruments and Hedging Activities - Balance Sheet Offsetting Disclosure (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Offsetting [Abstract]	'	'
Gross Amount of Recognized Assets	$32	'
Gross Amount Offset in the Statement of Financial Position, Derivative Assets	'	'
Net Amount of Assets Presented in the Statement of Financial Position	32	'
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments, Derivative Assets	32	'
Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Received, Derivative Assets	'	'
Derivative Assets, Net Amount	'	'
Gross Amount of Recognized Liabilities	44	353
Gross Amount Offset in the Statement of Financial Position, Derivative Liabilities	'	'
Net Amount of Liabilities Presented in the Statement of Financial Position	44	353
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments, Derivative Liabilities	44	353
Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Received, Derivative Liabilities	'	'
Derivative liabilities, Net Amount	'	'

Derivative_Instruments_and_Hed5

Derivative Instruments and Hedging Activities - Gains and Losses Related to Derivative Contracts Designated as Hedging Instruments (Detail) (Cash Flow Hedging [Member], Foreign currency forward contracts [Member], USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Cash Flow Hedging [Member] | Foreign currency forward contracts [Member]	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Pretax Gain (Loss) Recognized in Comprehensive Income on Effective Portion of Derivative	($32)	($300)	$279	($352)
Pretax Gain (Loss) Recognized in Income on Effective Portion of Derivative as a Result of Reclassification from Accumulated Other Comprehensive Loss	66	-27	131	-19
Gain (Loss) on Ineffective Portion of Derivative and Amount Excluded from Effectiveness Testing Recognized in Income	$3	($44)	($50)	($138)

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended
	Jun. 30, 2007	Sep. 30, 2013
Commitments And Contingencies Disclosure [Abstract]	'	'
Company made payments to Lower Willamette Group as interim settlement	$175,000	'
Maximum amount anticipated to spend for further Source Control work	'	100,000
Adjustment related to contingency liability in Portland Harbor matters	'	0
Total stand by letters of credit	'	$3,100,000

Segment_Information_Additional

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013
	Segment
Segment Reporting [Abstract]	'
Number of reportable segments	2

Segment_Information_Segment_In

Segment Information - Segment Information Report of Statements of Operations (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]	'	'	'	'
Net sales	$103,022	$115,099	$360,357	$388,315
Gross profit	8,812	11,600	45,684	41,677
Operating income (loss)	2,840	4,029	27,040	20,178
Water Transmission [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net sales	46,835	63,487	183,596	180,968
Gross profit	7,932	9,681	39,927	27,529
Operating income (loss)	6,306	6,969	34,838	21,123
Tubular Products [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net sales	56,187	51,612	176,761	207,347
Gross profit	880	1,919	5,757	14,148
Operating income (loss)	93	1,134	3,644	11,981
Corporate [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Operating income (loss)	($3,559)	($4,074)	($11,442)	($12,926)

Sharebased_Compensation_Additi

Share-based Compensation - Additional Information (Detail) (USD $)	9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
	OptionPlan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Number of inactive stock option plans	1	'
Number of active stock incentive plans	1	'
Unrecognized compensation expense	$4.90	'
Expected period of compensation expense recognition	'1 year 10 months 24 days	'
Total intrinsic value	$0.10	'
RSUs and PSAs at target level of performance included in unvested balance	198,000	'
Minimum performance awards issued multiplier	0.00%	'
Maximum performance awards issued multiplier	200.00%	'
Fair market value of stock awards used in calculation of compensation expense, grant date	$27.49	$23.40
Restricted Stock Units and Performance Awards [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Vesting period of PSAs	'3 years	'
Minimum [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Vesting period of PSAs	'2 years	'
Maximum [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Vesting period of PSAs	'3 years	'
Director [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Stock awards granted to non-employee directors	4,912	4,807

Sharebased_Compensation_Summar

Share-based Compensation - Summary of Share-Based Compensation Expense (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Share-based compensation expense	$877	$925	$2,167	$2,199
Cost of sales [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Share-based compensation expense	199	145	466	287
Selling, general and administrative expenses [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Share-based compensation expense	$678	$780	$1,701	$1,912

Sharebased_Compensation_Schedu

Share-based Compensation - Schedule of Share-Based Compensation, Stock Options, Activity (Detail) (USD $)	9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Options Outstanding, Beginning Balance	47,000
Options Outstanding, granted	'
Options Outstanding, exercised or exchanged	-7,000
Options Outstanding, canceled	'
Options Outstanding, Ending Balance	40,000
Options Outstanding, Exercisable	40,000
Options outstanding, Weighted Average Exercise Price per Share, Beginning Balance	$23.19
Options granted, Weighted Average Exercise Price per Share	'
Options exercised or exchanged, Weighted Average Exercise Price per Share	$10.31
Options canceled, Weighted Average Exercise Price per Share	'
Weighted Average Exercise Price per Share, Ending Balance	$25.44
Exercisable, Weighted Average Exercise Price per Share	$25.44
Weighted Average Remaining Contractual Life (in years), Ending balance	'4 years 10 months 24 days
Weighted Average Remaining Contractual Life (in years), Exercisable	'4 years 10 months 24 days
Options outstanding, Aggregate Intrinsic Value, Ending Balance	$309
Aggregate Intrinsic Value, Exercisable	$309

Sharebased_Compensation_Summar1

Share-based Compensation - Summary of Status of Company's RSUs and PSAs (Detail) (Restricted Stock Units and Performance Awards [Member], USD $)	9 Months Ended
	Sep. 30, 2013
Restricted Stock Units and Performance Awards [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Unvested RSUs and PSAs, Beginning Balance	243,141
RSUs and PSAs granted	122,878
RSUs and PSAs vested	-92,930
RSUs and PSAs canceled	-13,521
Unvested RSUs and PSAs, Ending Balance	259,568
Weighted Average Grant Date Fair Value, Unvested RSUs and PSAs, Beginning Balance	$26.11
Weighted Average Grant Date Fair Value, RSUs and PSAs granted	$33.97
Weighted Average Grant Date Fair Value, RSUs and PSAs vested	$23.59
Weighted Average Grant Date Fair Value, RSUs and PSAs canceled	$26.86
Weighted Average Grant Date Fair Value, RSUs and PSAs, Ending Balance	$30.69

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Income Tax Disclosure [Abstract]	'	'	'	'	'
Unrecognized tax benefits	$5.60	'	$5.60	'	$5.20
Expected change in unrecognized tax benefit	2.2	'	2.2	'	'
Income taxes at estimated effective tax (benefit) rates	42.30%	25.30%	33.40%	26.50%	'
Research and Development Tax Credit	'	$1.80	'	'	'
Federal statutory rate	35.00%	35.00%	'	35.00%	'

Earnings_per_Share_Earnings_pe

Earnings per Share - Earnings per Basic and Diluted Weighted Average Common Share Outstanding (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share Basic And Diluted [Abstract]	'	'	'	'
Net income	$1,016	$3,396	$16,083	$11,734
Basic weighted-average common shares outstanding	9,449	9,383	9,443	9,375
Effect of potentially dilutive common shares	68	116	55	83
Diluted weighted-average common shares outstanding	9,517	9,499	9,498	9,458
Earnings per basic common share	$0.11	$0.36	$1.70	$1.25
Earnings per diluted common share	$0.11	$0.36	$1.69	$1.24
Antidilutive shares not included in diluted common share calculation	93	96	97	120

Changes_in_Accumulated_Other_C2

Changes in Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Accumulated other comprehensive income (loss), Beginning Balance	'	'	($2,273)	'
Other comprehensive income before reclassifications	'	'	175	'
Amounts reclassified from accumulated other comprehensive income (loss)	'	'	112	'
Other comprehensive income (loss), net of tax	3	-109	287	69
Accumulated other comprehensive income (loss), Ending Balance	-1,986	'	-1,986	'
Defined Benefit Pension Items [Member]	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Accumulated other comprehensive income (loss), Beginning Balance	'	'	-2,188	'
Other comprehensive income before reclassifications	'	'	'	'
Amounts reclassified from accumulated other comprehensive income (loss)	'	'	194	'
Other comprehensive income (loss), net of tax	'	'	194	'
Accumulated other comprehensive income (loss), Ending Balance	-1,994	'	-1,994	'
Gains (Losses) on Cash Flow Hedges [Member]	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Accumulated other comprehensive income (loss), Beginning Balance	'	'	-85	'
Other comprehensive income before reclassifications	'	'	175	'
Amounts reclassified from accumulated other comprehensive income (loss)	'	'	-82	'
Other comprehensive income (loss), net of tax	'	'	93	'
Accumulated other comprehensive income (loss), Ending Balance	$8	'	$8	'

Changes_in_Accumulated_Other_C3

Changes in Accumulated Other Comprehensive Loss - Schedule of Effect on Net Income of Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Cost of sales	($94,210)	($103,499)	($314,673)	($346,638)
Net sales	103,022	115,099	360,357	388,315
Tax (expense) benefit	-746	686	-8,080	-4,044
Net of tax	1,016	3,396	16,083	11,734
Amount reclassified from Accumulated Other Comprehensive Income (Loss) [Member]	'	'	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Net of tax	'	'	-112	'
Amount reclassified from Accumulated Other Comprehensive Income (Loss) [Member] | Defined Benefit Pension Items [Member]	'	'	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Cost of sales	'	'	-295	'
Tax (expense) benefit	'	'	101	'
Net of tax	'	'	-194	'
Amount reclassified from Accumulated Other Comprehensive Income (Loss) [Member] | Gains (Losses) on Cash Flow Hedges [Member]	'	'	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Net sales	'	'	131	'
Tax (expense) benefit	'	'	-49	'
Net of tax	'	'	$82	'