Stepan (SCL) 10-K 27 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	SCL
Entity Registrant Name	STEPAN CO
Entity Central Index Key	94,049
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		22,514,141
Entity Public Float			$ 1,715,568,314

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net Sales (Note 1)	[1]	$ 1,925,007,000	$ 1,766,166,000	$ 1,776,167,000
Cost of Sales		1,586,742,000	1,427,621,000	1,467,926,000
Gross Profit		338,265,000	338,545,000	308,241,000
Operating Expenses:
Selling (Note 1)		54,271,000	57,212,000	55,522,000
Administrative (Note 1)		76,041,000	75,185,000	76,048,000
Research, development and technical services (Note 1)		53,867,000	56,086,000	50,243,000
Deferred compensation expense		4,857,000	16,805,000	6,500,000
Total Operating expenses		189,036,000	205,288,000	188,313,000
Gain on sale of product line				2,862,000
Business restructuring and asset impairments (Note 22)		(3,069,000)	(7,064,000)
Operating Income		146,160,000	126,193,000	122,790,000
Other Income (Expense):
Interest, net (Note 6)		(11,444,000)	(13,205,000)	(14,533,000)
Loss from equity in joint ventures (Notes 1 and 25)				(6,985,000)
Other, net (Note 8)		4,521,000	828,000	1,584,000
Nonoperating Income (Expense), Total		(6,923,000)	(12,377,000)	(19,934,000)
Income Before Provision for Income Taxes		139,237,000	113,816,000	102,856,000
Provision for Income Taxes (Note 9)		47,690,000	27,618,000	26,819,000
Net Income		91,547,000	86,198,000	76,037,000
Net (Income) Loss Attributable to Noncontrolling Interests (Note 1)		31,000	(7,000)	(69,000)
Net Income Attributable to Stepan Company		$ 91,578,000	$ 86,191,000	$ 75,968,000
Net Income Per Common Share Attributable to Stepan Company (Note 18):
Basic		$ 3.99	$ 3.78	$ 3.34
Diluted		$ 3.92	$ 3.73	$ 3.32
Shares Used to Compute Net Income Per Common Share Attributable to Stepan Company (Note 18):
Basic		22,946	22,793	22,730
Diluted		23,377	23,094	22,858
[1]	Net sales are attributed to countries based on the location of the Company facility making the sales.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net Income	$ 91,547	$ 86,198	$ 76,037
Other Comprehensive Income (Loss):
Foreign currency translation adjustments (Note 19)	26,293	(8,533)	(45,490)
Defined benefit pension plans:
Net actuarial gain (loss) arising in period (net of taxes of $771, $3,391, and $568 for 2017, 2016 and 2015, respectively)	(582)	3,818	1,311
Amortization of prior service cost included in pension expense (net of taxes of $4, $4, and $6 for 2017, 2016 and 2015, respectively)	10	10	11
Amortization of actuarial loss included in pension expense (net of taxes of $1,240, $1,301, and $1,755 for 2017, 2016 and 2015, respectively)	2,269	2,207	3,002
Net defined benefit pension plan activity (Note 19)	1,697	6,035	4,324
Cash flow hedges:
Losses arising in period (net of taxes of $0, $9 , and $26 in 2017, 2016 and 2015, respectively)		(19)	(49)
Reclassifications to income in period (net of taxes of $0, $28, and $8 in 2017, 2016 and 2015, respectively)	(9)	45	5
Net cash flow hedge activity (Note 19)	(9)	26	(44)
Other Comprehensive Income (Loss)	27,981	(2,472)	(41,210)
Comprehensive Income	119,528	83,726	34,827
Comprehensive (Income) Loss Attributable to Noncontrolling Interests	(48)	88	(2)
Comprehensive Income Attributable to Stepan Company	$ 119,480	$ 83,814	$ 34,825

Consolidated Statements of Com4

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net actuarial loss arising in period, tax	$ 771	$ 3,391	$ 568
Amortization of prior service cost included in pension expense, tax	4	4	6
Amortization of actuarial loss included in pension expense, tax	1,240	1,301	1,755
Losses arising in period, tax	0	(9)	(26)
Reclassifications to income in period, tax	$ 0	$ 28	$ 8

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Cash and cash equivalents	$ 298,894	$ 225,743
Receivables, less allowances of $10,116 in 2017 and $9,755 in 2016	293,541	263,408
Inventories (Note 5)	172,748	173,663
Other current assets	23,553	22,727
Total current assets	788,736	685,541
Property, Plant and Equipment:
Land	17,136	15,779
Buildings and improvements	203,879	184,773
Machinery and equipment	1,324,415	1,241,838
Construction in progress	57,856	71,088
Property, Plant and Equipment, Gross	1,603,286	1,513,478
Less: accumulated depreciation	(1,004,843)	(930,764)
Property, plant and equipment, net	598,443	582,714
Goodwill, net (Note 4)	25,118	25,308
Other intangible assets, net (Note 4)	18,538	22,339
Long-term investments (Note 2)	28,270	24,055
Other non-current assets	11,756	13,933
Total Assets	1,470,861	1,353,890
Current Liabilities:
Current maturities of long-term debt (Note 6)	22,500	28,154
Accounts payable	204,977	158,316
Accrued liabilities (Note 14)	92,776	110,795
Total current liabilities	320,253	297,265
Deferred income taxes (Note 9)	10,962	12,497
Long-term debt, less current maturities (Note 6)	268,299	288,859
Other non-current liabilities (Note 15)	130,433	119,353
Commitments and Contingencies (Note 16)
Equity (Note 10):
Common stock, $1 par value; authorized 60,000,000 shares; issued 26,070,787 shares in 2017 and 25,894,782 shares in 2016	26,071	25,895
Additional paid-in capital	170,408	158,042
Accumulated other comprehensive loss (Note 19)	(99,563)	(127,465)
Retained earnings	721,741	649,070
Less: Common treasury stock, at cost, 3,561,509 shares in 2017 and 3,470,084 shares in 2016	(78,561)	(70,938)
Total Stepan Company stockholders’ equity	740,096	634,604
Noncontrolling interests	818	1,312
Total equity	740,914	635,916
Total Liabilities and Equity	$ 1,470,861	$ 1,353,890

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Allowances	$ 10,116	$ 9,755
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares issued	26,070,787	25,894,782
Treasury stock, shares	3,561,509	3,470,084

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows From Operating Activities
Net income	$ 91,547,000	$ 86,198,000	$ 76,037,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	79,022,000	74,967,000	66,985,000
Deferred compensation	4,857,000	16,805,000	6,500,000
Realized and unrealized gain on long-term investments	(4,178,000)	(152,000)	(21,000)
Stock-based compensation	7,151,000	12,618,000	4,374,000
Deferred income taxes	550,000	(8,426,000)	3,001,000
Other non-cash items	4,857,000	7,334,000	3,830,000
Changes in assets and liabilities, excluding effects of acquisitions:
Receivables, net	(16,358,000)	(17,180,000)	4,160,000
Inventories	5,655,000	(3,774,000)	2,851,000
Other current assets	(489,000)	1,471,000	(3,410,000)
Accounts payable and accrued liabilities	30,476,000	38,261,000	21,219,000
Pension liabilities	(1,960,000)	607,000	932,000
Environmental and legal liabilities	(1,142,000)	4,561,000	(1,398,000)
Deferred revenues	(1,125,000)	(1,128,000)	(1,345,000)
Net Cash Provided By Operating Activities	198,863,000	212,162,000	183,715,000
Cash Flows From Investing Activities
Expenditures for property, plant and equipment	(78,613,000)	(103,076,000)	(119,349,000)
Business acquisitions, net of cash acquired (Note 20)	(4,339,000)	(23,510,000)	(5,133,000)
Proceeds from sale of product line (Note 21)			3,262,000
Other, net	269,000	(3,935,000)	(4,750,000)
Net Cash Used In Investing Activities	(82,683,000)	(130,521,000)	(125,970,000)
Cash Flows From Financing Activities
Revolving debt and bank overdrafts, net	(6,008,000)	1,292,000	(26,217,000)
Other debt borrowings			100,000,000
Other debt repayments	(20,714,000)	(15,069,000)	(13,098,000)
Dividends paid	(18,907,000)	(17,329,000)	(16,300,000)
Company stock repurchased	(6,000,000)	(2,408,000)	(2,000,000)
Stock option exercises	3,370,000	4,017,000	777,000
Other, net	(2,238,000)	(275,000)	(673,000)
Net Cash Provided By (Used In) Financing Activities	(50,497,000)	(29,772,000)	42,489,000
Effect of Exchange Rate Changes on Cash	7,468,000	(2,269,000)	(9,306,000)
Net Increase in Cash and Cash Equivalents	73,151,000	49,600,000	90,928,000
Cash and Cash Equivalents at Beginning of Year	225,743,000	176,143,000	85,215,000
Cash and Cash Equivalents at End of Year	298,894,000	225,743,000	176,143,000
Supplemental Cash Flow Information
Cash payments of income taxes, net of refunds	25,661,000	30,581,000	21,784,000
Cash payments of interest	$ 13,889,000	$ 14,730,000	$ 11,943,000

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Noncontrolling Interests' Equity [Member]
Beginning Balance at Dec. 31, 2014	$ 536,944	$ 25,640	$ 139,573	$ (66,262)	$ (83,945)	$ 520,540	$ 1,398
Issuance of common stock under stock option plan	777	45	732
Purchase of common stock	(2,000)			(2,000)
Stock-based and deferred compensation	3,694	24	3,854	(184)
Net income	76,037					75,968	69
Other comprehensive income	(41,210)				(41,143)		(67)
Cash dividends paid:
Common stock	(16,300)					(16,300)
Non-qualified stock option and stock award income tax benefit	442		442
Ending Balance at Dec. 31, 2015	558,384	25,709	144,601	(68,446)	(125,088)	580,208	1,400
Issuance of common stock under stock option plan	4,017	168	3,849
Purchase of common stock	(2,408)			(2,408)
Stock-based and deferred compensation	9,526	18	9,592	(84)
Net income	86,198					86,191	7
Other comprehensive income	(2,472)				(2,377)		(95)
Cash dividends paid:
Common stock	(17,329)					(17,329)
Ending Balance at Dec. 31, 2016	635,916	25,895	158,042	(70,938)	(127,465)	649,070	1,312
Issuance of common stock under stock option plan	3,370	104	3,266
Purchase of common stock	(6,000)			(6,000)
Stock-based and deferred compensation	7,549	72	9,100	(1,623)
Net income	91,547					91,578	(31)
Other comprehensive income	27,981				27,902		79
Cash dividends paid:
Common stock	(18,907)					(18,907)
Payment of cash dividends to noncontrolling interest	(542)						(542)
Ending Balance at Dec. 31, 2017	$ 740,914	$ 26,071	$ 170,408	$ (78,561)	$ (99,563)	$ 721,741	$ 818

Consolidated Statements of Equ9

Consolidated Statements of Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of shares of common stock issued under stock option plan	104,277	167,675	45,289
Number of common stock shares purchased	76,790	43,835	41,915
Common stock	$ 0.86	$ 0.78	$ 0.73
Common Stock [Member]
Number of shares of common stock issued under stock option plan	104,277	167,675	45,289
Additional Paid-in Capital [Member]
Number of shares of common stock issued under stock option plan	104,277	167,675	45,289
Treasury Stock [Member]
Number of common stock shares purchased	76,790	43,835	41,915

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. Summary of Significant Accounting Policies Nature of Operations Stepan Company (the Company) operations consist predominantly of the production and sale of specialty and intermediate chemicals, which are sold to other manufacturers for use in a variety of end products. Principal markets for all products are manufacturers of cleaning and washing compounds (including detergents, shampoos, fabric softeners, toothpastes and household cleaners), paints, cosmetics, food, beverages, nutritional supplements, agricultural products, plastics, furniture, automotive equipment, insulation and refrigeration. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (GAAP) requires Company management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Principles of Consolidation The consolidated financial statements include the accounts of the Company and all wholly and majority-owned subsidiaries in which the Company exercises controlling influence. The equity method is used to account for investments in which the Company exercises significant but noncontrolling influence. Intercompany balances and transactions are eliminated in consolidation. The Company has an 80 percent ownership interest in the Nanjing Stepan Jinling Chemical Limited Liability Company (a joint venture) and exercises controlling influence over the entity. Therefore, Nanjing Stepan Jinling Chemical Limited Liability Company’s accounts are included in the Company’s consolidated financial statements. The partner’s interest in the joint venture’s net income is reported in the net income attributable to noncontrolling interests line of the consolidated statements of income. The partner’s interest in the net assets of the joint venture is reported in the noncontrolling interests line (a component of equity separate from Company equity) of the consolidated balance sheets. Prior to 2016, the Company and Nalco Company (a subsidiary of Ecolab Inc.) equally owned and controlled TIORCO, LLC, a joint venture operated out of Denver, Colorado. In October 2015, the Company and Nalco Company made the decision to dissolve TIORCO, LLC. See Note 25 for information regarding the dissolution of the joint venture. Prior to the dissolution of the joint venture, the Company’s investment in TIORCO, LLC was accounted for using the equity method and was included in the other non-current assets line on the consolidated balance sheets. The Company’s share of joint venture’s net earnings was included in the loss from equity in joint ventures line of the consolidated statements of income. Cash and Cash Equivalents The Company considers all highly liquid investments with purchased maturities of three months or less to be cash equivalents. At December 31, 2017, the Company’s cash and cash equivalents totaled $298.9 million including $15.1 million in a money market fund, each of which was rated AAAm by Standard and Poor’s. Cash in U.S. demand deposit accounts totaled $131.9 million and cash of the Company’s non-U.S. subsidiaries held outside the U.S. totaled $151.9 million as of December 31, 2017. Receivables and Credit Risk Receivables are stated net of allowances for doubtful accounts and other allowances and primarily include trade receivables from customers, as well as nontrade receivables from suppliers, governmental tax agencies and others. The Company is exposed to credit risk on accounts receivable balances. This risk is mitigated by the Company’s large, diverse customer base, which is dispersed over various geographic regions and industrial sectors. No single customer comprised more than 10 percent of the Company’s consolidated net sales in 2017, 2016 or 2015. The Company maintains allowances for potential credit losses. Specific customer allowances are recorded when a review of customer creditworthiness and current economic conditions indicate that collection is doubtful. The Company also maintains other customer allowances that occur in the normal course of business. Such allowances are based on historical averages and trade receivable levels. The following is an analysis of the allowance for doubtful accounts and other accounts receivable allowances for the years ended December 31, 2017, 2016 and 2015: (In thousands) 2017 2016 2015 Balance at January 1 $ 9,755 $ 8,046 $ 10,011 Provision charged to income 45 1,917 1,106 Accounts written off, net of recoveries 316 (208 ) (3,071 ) Balance at December 31 $ 10,116 $ 9,755 $ 8,046 Inventories Inventories are valued at cost, which is not in excess of market value, and include material, labor and plant overhead costs. The last-in, first-out (LIFO) method is used to determine the cost of the Company’s U.S. inventories. The first-in, first-out (FIFO) method is used for all other inventories. Inventories priced at LIFO as of December 31, 2017 and 2016, accounted for 69 and 66 Property, Plant and Equipment Depreciation of property, plant and equipment is provided on a straight-line basis over the estimated useful lives of the assets. Lives used for calculating depreciation are generally 30 years for buildings and 15 years for building improvements. For assets classified as machinery and equipment, lives generally used for calculating depreciation expense range from 10 to 15 years for manufacturing equipment, five to 10 years for furniture and fixtures, three to five years for vehicles and three to 10 years for computer equipment and software. Manufacturing of chemicals is capital intensive with a large majority of the assets included in machinery and equipment representing manufacturing equipment. Major renewals and betterments are capitalized in the property accounts, while maintenance and repairs ($51,926,000 Included in the computer equipment and software component of machinery and equipment are costs related to the acquisition and development of internal-use software. Capitalized costs for internal-use software include external direct costs of materials and services consumed in obtaining and developing the software. For development projects where major internal resources are committed, payroll and payroll-related costs incurred during the application development phase of the project are also capitalized. The capitalized costs are amortized over the useful lives of the software, which are generally three to 10 years. Costs incurred in the preliminary project phase are expensed. Interest charges on borrowings applicable to major construction projects are capitalized. Property, plant and equipment assets are tested for impairment when events indicate that impairment may have occurred. See Note 22 for 2016 asset impairments. Fair Value Measurements GAAP defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Furthermore, GAAP establishes a framework, in the form of a three-level hierarchy, for measuring fair value that prioritizes the inputs to valuation techniques used to measure fair value. The following describes the hierarchy levels: Level 1 - quoted prices in active markets for identical assets and liabilities. Level 2 - inputs other than quoted prices included within Level 1 that are directly or indirectly observable for the asset or liability, such as quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets and liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data. Level 3 - unobservable inputs which reflect the entity’s own assumptions about the assumptions market participants use in pricing the assets and liabilities. The Company applies the fair value measurement provisions of GAAP to any of its financial assets and liabilities that are carried at fair value on the consolidated balance sheets (see Note 2), its outstanding debt for disclosure purposes (also Note 2) and its pension plan assets (see Note 13). The Company also applies the fair value measurement requirements to nonrecurring fair value measurements of nonfinancial assets and liabilities recorded in conjunction with business combinations and as part of impairment reviews for goodwill and other long-lived assets. Revenue Recognition Revenue is recognized upon shipment of goods to customers at the time title and risk of loss pass to the customer. In a majority of instances this occurs when goods are provided to a carrier for shipment. For arrangements where the Company consigns product to a customer location, revenue is recognized when the customer uses the inventory. The Company records shipping and handling billed to a customer in a sales transaction as revenue. Costs incurred for shipping and handling are reported in cost of sales. Volume and cash discounts due customers are estimated and recorded in the same period as the sales to which the discounts relate and reported as reductions of revenue in the consolidated statements of income. Cost of Sales Cost of sales comprises raw material costs (including inbound freight expense to deliver the raw materials), manufacturing plant labor expenses and various manufacturing overhead expenses, such as utility, maintenance, operating supply, amortization and manufacturing asset depreciation expenses. Cost of sales also includes outbound shipping and handling expenses, inter-plant transfer costs, warehouse expenses and rail car rental expenses. Operating Expenses Selling expense comprises salary and the related fringe benefit expenses for marketing and sales personnel and operating costs, such as outside agent commissions, automobile rental and travel-related expenses, which support the sales and marketing functions. Bad debt charges and any depreciation expenses related to marketing assets (e.g., computers) are also classified as selling expense. Administrative expense comprises salary and the related fringe benefit expenses and operating costs for the Company’s various administrative functions, which include information services, finance, legal, and human resources. Environmental remediation expenses are also classified as administrative expense. The Company’s research and development costs are expensed as incurred. These expenses are aimed at discovery and commercialization of new knowledge with the intent that such effort will be useful in developing a new product or in bringing about a significant improvement to an existing product or process. Total research and development expenses were $33,169,000, $34,856,000, and $30,315,000 Compensation expense or income related to the Company’s deferred compensation plans is presented in the deferred compensation expense line in the Consolidated Statements of Income. Environmental Expenditures Environmental expenditures that relate to current operations are expensed in cost of sales. Expenditures that mitigate or prevent environmental contamination and that benefit future operations are capitalized as assets and depreciated on a straight-line basis over the estimated useful lives of the assets, which are typically 10 years. Estimated future expenditures that relate to an existing condition caused by past operations, and which do not contribute to current or future revenue generation, are recorded as liabilities, with the corresponding charge recorded in administrative expenses, when environmental assessments and/or remedial efforts are probable and the cost or range of possible costs can be reasonably estimated. When no amount within the range is a better estimate than any other amount, the minimum amount in the range is accrued. Some of the factors on which the Company bases its estimates include information provided by feasibility studies, potentially responsible party negotiations and the development of remedial action plans. Legal costs related to environmental matters are expensed as incurred (see Note 16 for environmental contingencies). Goodwill and Other Intangible Assets The Company’s intangible assets include patents, agreements not to compete, trademarks, customer lists and relationships, technological and manufacturing know-how, supply contracts and goodwill, all of which were acquired as part of business or product line acquisitions. Intangible assets other than goodwill are determined to have either finite or indefinite useful lives. The Company currently has no indefinite-life intangible assets other than goodwill. The values for intangible assets with finite lives are amortized over the useful lives of the assets. Currently, the useful lives for the Company’s finite-lived intangible assets are as follows: patents – 10-15 years; non-compete agreements – five years; trademarks – 11 years; customer relationships – 10-13 years; supply contracts – four years and know-how – eight years. In addition, finite-life intangible assets are tested for impairment when events or changes in circumstances indicate that the carrying value of an intangible asset may not be recoverable. Goodwill is not amortized but is tested for impairment at least annually or more frequently if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit to which goodwill relates below the reporting unit’s carrying value. See Note 4 for detailed information about goodwill and other intangible assets. Income Taxes Income taxes are accounted for under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. Deferred tax assets are recognized to the extent that we believe these assets are more likely than not to be realized. In making such a determination, we consider all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If we determine that we would be able to realize our deferred tax assets in the future in excess of their net recorded amount, we would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. Uncertain tax positions are recorded in accordance with ASC 740 on the basis of a two-step process whereby (1) we determine whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, we recognize the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within the income tax expense line in the accompanying Consolidated Statement of Operations. Accrued interest and penalties are included within the related tax liability line in the Consolidated Balance Sheet. The SEC staff issued Staff Accounting Bulletin 118 (“SAB 118”), which provides guidance on accounting for the tax effects of the U.S. Tax Cuts and Jobs Act (“Tax Act”). SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Act for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Act is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the Tax Act. See Note 9 for detailed information about income taxes including SAB 118 disclosures. Translation of Foreign Currencies For the Company’s consolidated foreign subsidiaries whose functional currency is the local foreign currency, assets and liabilities are translated into U.S. dollars at exchange rates in effect at year end and revenues and expenses are translated at average exchange rates for the year. Any resulting translation adjustments are included in the consolidated balance sheets in the accumulated other comprehensive loss line of stockholders’ equity. Gains or losses on foreign currency transactions are reflected in the other, net caption of the consolidated statements of income. The Company has two foreign subsidiaries whose functional currencies are the U.S. dollar. For these subsidiaries, nonmonetary assets and liabilities are translated at historical rates, monetary assets and liabilities are translated at exchange rates in effect at year end, revenues and expenses are translated at average exchange rates for the year and translation gains and losses are included in the other, net caption of the consolidated statements of income. Stock-Based Compensation The Company grants stock options, stock awards (including performance-based stock awards) and stock appreciation rights (SARs) to certain employees under its incentive compensation plans. The Company calculates the fair values of stock options, stock awards and SARs on the date such instruments are granted. The fair values of the stock options and stock awards are then recognized as compensation expense over the vesting periods of the instruments. The Company’s SARs granted before 2015 settle in cash. The cash-settled SARs are accounted for as liabilities that must be re-measured at fair value at the end of each reporting period. Compensation expense for each reporting period is calculated as the period-to-period change (or portion of the change, depending on the proportion of the vesting period that has been completed at the reporting date) in the fair value of the cash-settled SARs. SARs granted subsequent to 2014 are settled in shares of Company common stock. Compensation expense for the stock-settled SARs is calculated in the same way as compensation expense for stock options. See Note 11 for detailed information about the Company’s stock-based compensation. Earnings Per Share Basic earnings per share amounts are computed as net income attributable to the Company divided by the weighted-average number of common shares outstanding. Diluted earnings per share amounts are based on the weighted-average number of common shares outstanding plus the weighted-average of net common shares (under the treasury stock method) that would be outstanding assuming the exercise of outstanding stock options and stock-settled SARs, the vesting of unvested stock awards that have no performance or market condition and the issuance of contingent performance stock awards. See Note 18 for detailed information about the Company’s earnings per share calculations. Comprehensive Income and Accumulated Other Comprehensive Income Comprehensive income includes net income and all other non-owner changes in equity that are not reported in net income. Comprehensive income is disclosed in the consolidated statements of comprehensive income. Accumulated other comprehensive income (AOCI) is reported as a component of stockholders’ equity in the Company’s consolidated balance sheets. See Note 19 for detailed information regarding changes in the Company’s AOCI and reclassifications out of AOCI to income. Segment Reporting The Company reports financial and descriptive information about its reportable operating segments. Operating segments are components of the Company that have separate financial information that is regularly evaluated by the chief operating decision maker to assess segment performance and allocate resources. The Company discloses segment revenue, operating income, assets, capital expenditures and depreciation and amortization expenses. Enterprise-wide financial information about the geographic locations in which the Company earns revenues and holds assets is also disclosed (see Note 17). Derivative Instruments Derivative instruments are recognized in the consolidated balance sheets as either assets or liabilities measured at fair value. For derivative instruments that are not designated as hedging instruments, changes in the fair values of the derivative instruments are recognized currently in earnings. For derivative instruments designated as hedging instruments, depending on the nature of the hedge, changes in the fair values of the derivative instruments are either offset in earnings against changes in the fair values of the hedged items or recognized in AOCI until the hedged transaction is recognized in earnings. At the time a hedging relationship is designated, the Company establishes the method it will use for assessing the effectiveness of the hedge and the measurement approach for determining the ineffective aspect of the hedge. Company policy prohibits the use of derivative instruments for trading or speculative purposes. See Note 3 for further information regarding the Company’s use of derivatives. At December 31, 2017, the Company held open forward contracts for the purchase of 0.8 Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-9, Revenue from Contracts with Customers (Topic 606) Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date In February 2016, the FASB issued ASU No. 2016-2, Leases (Topic 842) In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory In January 2017, the FASB issued ASU No. 2017-4, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment In March 2017, the FASB issued ASU No. 2017-7, Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities In January 2018, the FASB issued ASU No. 2018-01, Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	2. Fair Value Measurements The following were the financial instruments held by the Company at December 31, 2017 and 2016, and the methods and assumptions used to estimate the instruments’ fair values: Cash and cash equivalents Carrying value approximated fair value because of the short maturity of the instruments. Derivative assets and liabilities Derivative assets and liabilities include the foreign currency exchange and interest rate contracts discussed in Note 3. Fair value and carrying value were the same because the contracts were recorded at fair value. The fair values of the foreign currency contracts were calculated as the difference between the applicable forward foreign exchange rates at the reporting date and the contracted foreign exchange rates multiplied by the contracted notional amounts. The fair values of the interest rate swaps were calculated as the difference between the contracted swap rate and the current market replacement swap rate multiplied by the present value of one basis point for the notional amount of the contract. See the table that follows the financial instrument descriptions for the reported fair values of derivative assets and liabilities. Long-term investments Long-term investments included the mutual fund assets the Company held to fund a portion of its deferred compensation liabilities and all of its non-qualified supplemental executive defined contribution obligations (see the defined contribution plans section of Note 13). Fair value and carrying value were the same because the mutual fund assets were recorded at fair value in accordance with the FASB’s fair value option guidance. Fair values for the mutual funds were calculated using the published market price per unit at the reporting date multiplied by the number of units held at the reporting date. See the table that follows the financial instrument descriptions for the reported fair value of long-term investments. Debt obligations The fair value of debt with original maturities greater than one year comprised the combined present values of scheduled principal and interest payments for each of the various loans, individually discounted at rates equivalent to those which could be obtained by the Company for new debt issues with durations equal to the average life to maturity of each loan. The fair values of the remaining Company debt obligations approximated their carrying values due to the short-term nature of the debt. The Company’s fair value measurements for debt fall in level 2 of the fair value hierarchy. At December 31, 2017 and 2016, the fair values and related carrying values of debt, including current maturities, were as follows (the fair value and carrying value amounts are presented without regard to unamortized debt issuance costs of $987,000, and $1,141,000 December 31 (In thousands) 2017 2016 Fair value $ 293,272 $ 316,364 Carrying value 291,786 318,154 The following tables present financial assets and liabilities measured on a recurring basis at fair value as of December 31, 2017 and 2016, and the level within the fair value hierarchy in which the fair value measurement falls: (In thousands) December 2017 Level 1 Level 2 Level 3 Mutual fund assets $ 28,270 $ 28,270 $ — $ — Derivative assets: Foreign currency contracts 335 — 335 — Total assets at fair value $ 28,605 $ 28,270 $ 335 $ — Derivative liabilities: Foreign currency contracts $ 94 $ — $ 94 $ — (In thousands) December 2016 Level 1 Level 2 Level 3 Mutual fund assets $ 24,055 $ 24,055 $ — $ — Derivative assets: Foreign currency contracts 453 — 453 — Total assets at fair value $ 24,508 $ 24,055 $ 453 $ — Derivative liabilities: Foreign currency contracts $ 469 $ — $ 469 $ — Total liabilities at fair value $ 469 $ — $ 469 $ —

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments	3. Derivative Instruments The Company is exposed to certain risks relating to its ongoing business operations. The primary risk managed by the use of derivative instruments is foreign currency exchange risk. The Company holds forward foreign currency exchange contracts that are not designated as any type of accounting hedge as defined by U.S. generally accepted accounting principles. The Company uses these contracts to manage its exposure to exchange rate fluctuations on certain Company subsidiary cash, accounts receivable, accounts payable and other obligation balances that are denominated in currencies other than the entities’ functional currencies. The forward foreign exchange contracts are recognized on the balance sheet as either an asset or a liability measured at fair value. Gains and losses arising from recording the foreign exchange contracts at fair value are reported in earnings as offsets to the losses and gains reported in earnings arising from the re-measurement of the receivable and payable balances into the applicable functional currencies. At December 31, 2017 and 2016, the Company had open forward foreign currency exchange contracts, all with durations of one to three months, to buy or sell foreign currencies with a U.S. dollar equivalent of $41,196,629 and $33,372,000 The Company held no interest rate contracts at December 31, 2017 or December 31, 2016. The Company held an interest rate swap contract with a notional value of $ $3,724,000 at December 31, 2015. In the fourth quarter of 2016, the underlying loan that was hedged with the interest rate swap contract was paid in full, and the contract was terminated. The loss realized from the termination of the interest rate swap was immaterial. The fair values of the derivative instruments held by the Company on December 31, 2017, and December 31, 2016, are disclosed in Note 2. Derivative instrument gains and losses for the years ended December 31, 2017, 2016 and 2015, were immaterial. For amounts reclassified out of AOCI into earnings for the years ended December 31, 2017, 2016 and 2015, see Note 19.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	4. The changes in the carrying value of goodwill for the years ended December 31, 2017 and 2016, were as follows: Surfactants Segment Polymer Segment Specialty Products Segment Total (In thousands) 2017 2016 2017 2016 2017 2016 2017 2016 Balance as of January 1 Goodwill $ 22,958 $ 8,869 $ 5,334 $ 5,380 $ 483 $ 483 $ 28,775 $ 14,732 Accumulated impairment loss (3,467 ) (3,467 ) — — — — (3,467 ) (3,467 ) Goodwill, net 19,491 5,402 5,334 5,380 483 483 25,308 11,265 Goodwill acquired (a) — 14,327 — — — — — 14,327 Goodwill measurement period adjustment (a) (120 ) — — — — — (120 ) — Foreign currency translation (211 ) (238 ) 141 (46 ) — — (70 ) (284 ) Balance as of December 31 Goodwill 22,627 22,958 5,475 5,334 483 483 28,585 28,775 Accumulated impairment loss (3,467 ) (3,467 ) — — — — (3,467 ) (3,467 ) Goodwill, net $ 19,160 $ 19,491 $ 5,475 $ 5,334 $ 483 $ 483 $ 25,118 $ 25,308 (a) See Note 20 for information regarding the goodwill acquired in a business combination. The Company tests its goodwill balances for impairment in the second quarter of each calendar year. The 2017 and 2016 tests indicated no impairment. The following table presents the components of other intangible assets, all of which have finite lives, as of December 31, 2017 and 2016. The year-over-year changes in gross carrying values mainly resulted from the effects of foreign currency translation. Gross Carrying Value Accumulated Amortization December 31 December 31 (In thousands) 2017 2016 2017 2016 Other Intangible Assets: Patents $ 6,947 $ 6,947 $ 3,893 $ 3,294 Non-compete agreements 453 $ 461 113 $ 15 Trademarks 4,087 4,087 1,870 1,525 Customer lists 12,150 12,238 4,299 3,337 Supply contract 2,476 2,521 774 105 Know-how (a) 8,043 8,043 4,669 3,682 Total $ 34,156 $ 34,297 $ 15,618 $ 11,958 (a) Know-how includes intellectual property rights covering proprietary information, written formulae, trade secrets or secret processes, inventions and developmental products (whether patentable or not), discoveries, improvements, compositions, manufacturing processes, manuals, specifications and technical data Aggregate amortization expense for the years ended December 31, 2017, 2016 and 2015, was $3,711,000, $2,845,000, and $2,816,000 (In thousands) For year ended 12/31/18 $ 3,584 For year ended 12/31/19 3,584 For year ended 12/31/20 3,435 For year ended 12/31/21 2,025 For year ended 12/31/22 1,368

Inventories

Inventories	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventories	5. Inventories The composition of inventories was as follows: December 31 (In thousands) 2017 2016 Finished products $ 117,529 $ 127,597 Raw materials 55,219 46,066 Total inventories $ 172,748 $ 173,663 Inventories are primarily priced using the last-in, first-out (LIFO) inventory valuation method. If the first-in, first-out (FIFO) inventory valuation method had been used for all inventories, inventory balances would have been approximately $33,518,000 and $25,872,000 higher than reported at December 31, 2017 and 2016, respectively.

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt	6. Debt Debt comprised the following at December 31, 2017 and 2016: (In thousands) Maturity Dates December 31, 2017 December 31, 2016 Unsecured private placement notes 3.95% (net of unamortized debt issuance cost of $346 and $382 for 2017 and 2016, respectively) 2021-2027 $ 99,654 $ 99,618 3.86% (net of unamortized debt issuance cost of $343 and $390 for 2017 and 2016, respectively) 2019-2025 99,657 99,610 4.86% (net of unamortized debt issuance cost of $191 and $225 for 2017 and 2016, respectively) 2018-2023 55,523 64,775 5.88% (net of unamortized debt issuance cost of $95 and $116 for 2017 and 2016, respectively) 2018-2022 28,476 34,170 5.69% (net of unamortized debt issuance cost of $12 and $28 for 2017 and 2016, respectively) 2018 5,703 11,400 Debt of foreign subsidiaries Unsecured bank debt, foreign currency 2018 1,786 432 Secured bank debt, foreign currency 2018 — 7,008 Total debt $ 290,799 $ 317,013 Less current maturities 22,500 28,154 Long-term debt $ 268,299 $ 288,859 The majority of the Company’s long-term debt financing is composed of unsecured private placement notes issued to insurance companies, totaling $290,000,000 as of December 31, 2017. These notes are denominated in U.S. dollars and have fixed interest rates ranging from 3.86 percent to 5.88 percent. At inception, these notes had final maturities of 12 to 13 years with remaining amortization scheduled from 2018 to 2027. At December 31, 2017 the Company had a committed $125,000,000 multi-currency five-year revolving credit agreement. This unsecured facility was the Company’s primary source of short-term borrowings and the Company was able to draw on this agreement as needed to finance certain acquisitions, working capital and for general corporate purposes. This facility was scheduled to expire on July 10, 2019. On December 31, 2017, the Company had outstanding letters of credit of $4,677,000 and no borrowings under this agreement with $120,323,000 remaining available. Loans under the credit agreement in place at December 31, 2017 could have been incurred, at the discretion of the Company, with terms to maturity of 1 to 180 days. The Company may have chosen from several interest rate options, including (1) LIBOR applicable to each currency plus spreads ranging from 0.975 percent to 1.525 percent, depending on the Company’s leverage ratio or (2) the prime rate plus zero percent to 0.525 percent, depending on the leverage ratio. The credit agreement required the Company to pay a facility fee ranging from 0.150 percent to 0.350 percent, which also depended on the leverage ratio. The credit agreement required the maintenance of certain financial ratios and compliance with certain other covenants that are similar to the Company’s existing debt agreements, including net worth, interest coverage and leverage financial covenants and limitations on restricted payments, indebtedness and liens. In addition to the unsecured private placement notes and the revolving credit facility, the Company’s foreign subsidiaries had $1,786,000 of unsecured debt at December 31, 2017. The Company’s loan agreements in the U.S. and Philippines contain provisions, which, among others, require maintenance of certain financial ratios and place limitations on additional debt, investments and payment of dividends. Based on the loan agreement provisions that place limitations on dividend payments, unrestricted retained earnings (i.e., retained earnings available for dividend distribution) were $190,495,000 and $157,606,000 at December 31, 2017, and 2016, respectively. Debt at December 31, 2017, matures as follows: $22,500,000 in 2018; $29,286,000 in 2019; $29,286,000 in 2020; $43,572,000 in 2021; $43,572,000 Net interest expense for the years ended December 31, 2017, 2016 and 2015, comprised the following: (In thousands) 2017 2016 2015 Interest expense $ 14,428 $ 15,240 $ 15,488 Interest income (2,075 ) (1,247 ) (217 ) 12,353 13,993 15,271 Capitalized interest (909 ) (788 ) (738 ) Interest expense, net $ 11,444 $ 13,205 $ 14,533

Leased Properties

Leased Properties	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Leased Properties	7. Leased Properties The Company leases certain property and equipment (primarily transportation equipment, buildings and land) under operating leases, which are denominated in local currencies. Total rental expense was $10,807,000, $8,595,000, and $7,097,000 in 2017, 2016 and 2015, respectively. Consolidated Company minimum future rental payments under operating leases with initial or remaining noncancelable lease terms in excess of one year as of December 31, 2017, are: (In thousands) Year 2018 $ 8,950 2019 6,659 2020 5,967 2021 4,683 2022 4,099 Subsequent to 2022 20,173 Total minimum future rental payments $ 50,531

Other, Net

Other, Net	12 Months Ended
	Dec. 31, 2017
Other Income And Expenses [Abstract]
Other, Net	8. Other, Net Other, net in the consolidated statements of income included the following for the years ended December 31, 2017, 2016 and 2015: (In thousands) 2017 2016 2015 Foreign exchange gains (losses) $ (646 ) $ (14 ) $ 686 Investment income 989 690 877 Realized and unrealized gains on investments 4,178 152 21 Other, net $ 4,521 $ 828 $ 1,584

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	9. Income Taxes The provisions for taxes on income and the related income before taxes for the years ended December 31, 2017, 2016 and 2015, were as follows: (In thousands) 2017 2016 2015 Taxes on Income Federal Current $ 32,299 $ 18,811 $ 7,697 Deferred (1,744 ) (3,192 ) 3,890 State Current 1,764 2,273 1,559 Deferred 192 (1,171 ) (225 ) Foreign Current 13,077 14,960 14,562 Deferred 2,102 (4,063 ) (664 ) Total $ 47,690 $ 27,618 $ 26,819 Income before Taxes Domestic $ 72,662 $ 64,675 $ 48,721 Foreign 66,575 49,141 54,135 Total $ 139,237 $ 113,816 $ 102,856 On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (“Tax Act”). The Tax Act makes broad and complex changes to the U.S. tax code that affects the Company’s income tax provision for 2017, including, but not limited to, (1) a one-time transition tax (“Transition Tax”) on certain unrepatriated earnings of foreign subsidiaries that is payable over eight years and (2) bonus depreciation that will allow for full expensing of qualified property. The Tax Act also establishes new tax laws that will affect the Company’s income tax provision for 2018, including, but not limited to, (1) reduction of the U.S. federal corporate income tax rate; (2) a general elimination of U.S. federal income taxes on dividends from foreign subsidiaries; (3) a new provision designed to tax global intangible low-taxed income, which allows for the possibility of using foreign tax credits (FTCs) and a deduction of up to 50 percent to offset the income tax liability (subject to some limitations); (4) the creation of the base erosion anti-abuse tax, a new minimum tax; (5) limitations on the use of FTCs to reduce the U.S. income tax liability; (6) limitations on net operating losses (NOLs) generated after December 31, 2017, to 80 percent of taxable income; (7) a new limitation on deductible interest expense; (8) elimination of the corporate alternative minimum tax; (9) the repeal of the domestic production activity deduction; and (10) limitations on the deductibility of certain executive compensation. The variations between the effective and statutory U.S. federal income tax rates are summarized as follows: (In thousands) 2017 Amount % 2016 Amount % 2015 Amount % Federal income tax provision at statutory tax rate $ 48,733 35.0 $ 39,836 35.0 $ 36,000 35.0 State tax provision on income less applicable federal tax benefit 1,271 0.9 716 0.6 867 0.8 Foreign income taxed at different rates (8,075 ) (5.8 ) (6,325 ) (5.6 ) (5,060 ) (4.9 ) Repatriation of foreign earnings (1,054 ) (0.8 ) 14 — 21 — Unrecognized tax benefits (47 ) 0.0 23 — 1,536 1.5 Domestic production activities deduction (1,339 ) (1.0 ) (1,633 ) (1.4 ) (884 ) (0.9 ) Nontaxable foreign interest income (2,073 ) (1.5 ) (2,030 ) (1.8 ) (2,106 ) (2.0 ) U.S. tax reform, net impact (a) 14,807 10.7 — — — — Change in accounting method for depreciation (893 ) (0.6 ) — — — — Stock based compensation, excess tax benefits (b) (2,254 ) (1.6 ) (1,878 ) (1.7 ) — — U.S. tax credits (1,204 ) (0.9 ) (1,100 ) (1.0 ) (3,465 ) (3.4 ) Non-deductible expenses and other items, net (c) (182 ) (0.1 ) (5 ) 0.2 (90 ) — Total income tax provision $ 47,690 34.3 $ 27,618 24.3 $ 26,819 26.1 (a) Does not include state tax impacts, which are included in state tax provision on income less applicable federal tax benefit. (b) Excess tax benefits related to employee share-based payment transactions recognized in 2017 and 2016 resulting from the adoption of ASU No. 2016-9. There is no effect for 2015 because the recognition of excess tax benefits in the tax provision is to be done only on a prospective basis, beginning with the year of adopting the new guidance, which was 2016. (c) Certain 2016 and 2015 amounts have been reclassified to conform to the current year presentation. For various reasons that are discussed more fully below, we have not completed our accounting for the income tax effects of certain elements of the Tax Act. If we were able to make reasonable estimates of the effects of elements for which our analysis is not yet complete, we recorded provisional adjustments. If we were not yet able to make reasonable estimates of the impact of certain elements, we have not recorded any adjustments related to those elements and have continued accounting for them in accordance with ASC 740 on the basis of the tax laws in effect before the Tax Act. We were able to make reasonable estimates of certain effects and, therefore, recorded the following provisional adjustments: Reduction of US federal corporate tax rate: The Tax Act reduces the corporate tax rate to 21 percent, effective January 1, 2018. For certain of our deferred tax assets, we have recorded a provisional decrease of $31.8 million, which is offset by a provisional $36.3 million decrease in our deferred tax liabilities, resulting in a corresponding net adjustment to deferred income tax benefit of $4.5 million attributable to the rate reduction for the year ended December 31, 2017. While we are able to make a reasonable estimate of the impact of the reduction in corporate rate, it may be affected by other analyses related to the Tax Act, including, but not limited to, our calculation of deemed repatriation of deferred foreign income and the state tax effect of adjustments made to federal temporary differences. Deemed Repatriation Transition Tax: The Transition Tax is a tax on previously untaxed accumulated and current earnings and profits (E&P) of certain of our foreign subsidiaries. To determine the amount of the Transition Tax, we must determine, in addition to other factors, the amount of post-1986 E&P of the relevant subsidiaries, as well as the amount of non-U.S. income taxes paid on such earnings. We are able to make a reasonable estimate of the Transition Tax and recorded a provisional Transition Tax obligation of $19.4 million. However, we are continuing to gather additional information to more precisely compute the amount of the Transition Tax. Pursuant to the Tax Act, the Company will make an election to pay this liability in installments over eight years. Consequently, $18.1 million of this liability has been recorded as noncurrent taxes payable and $1.3 million as current taxes payable in the Company’s consolidated balance sheet as of December 31, 2017. We were not yet able to make reasonable estimates of the following effects and, therefore, no provisional adjustments were recorded: Global intangible low taxed income (“GILTI”): The Tax Act requires the Company to include certain income (GILTI) of its foreign subsidiaries in gross income. The amount of this inclusion is determined under complex rules, and depends, in part, on the character of income earned by the foreign subsidiaries, the tax bases of those subsidiaries’ assets and the amount of certain interest expenses. Under U.S. GAAP, we are allowed to make an accounting policy choice of either (1) treating taxes due on future income inclusions related to GILTI as a current-period expense when incurred (the “period cost method”) or (2) accounting for such amounts in measuring deferred taxes (the “deferred method”). Our selection of an accounting policy with respect to the new GILTI tax rules will depend, in part, on analyzing our global income to determine whether we expect to have future income inclusions related to GILTI and, if so, what the impact is expected to be. These determinations depend not only on our current structure and estimated future results of global operations but also our intent and ability to modify our structure and/or our business. Therefore, we have not made any adjustments or estimates related to any potential tax liabilities related to GILTI in our financial statements and have not made a policy decision regarding whether to record deferred tax liabilities related to GILTI. Cost recovery: We have not yet completed all of the computations necessary or completed an inventory of our 2017 expenditures that qualify for immediate expensing. Therefore, we have not made any adjustments or estimates related to any potential tax liabilities in our financial statements related to immediate expensing. Deductibility of Executive Compensation: The Tax Act amended certain aspects of Section 162(m) of the Internal Revenue Code (“Section 162(m)”), which generally disallows a tax deduction for annual compensation paid to “covered employees” in excess of $1 million, including eliminating an exception to the deduction limit for “qualified performance-based compensation”, effective for tax years beginning after December 31, 2017. The Tax Act provides for a grandfather provision, pursuant to which remuneration that is provided pursuant to a written binding contract in effect on November 2, 2017, and which has not been modified in any material respect on or after that date, will not be subject to the amendments made to Section 162(m) by the Tax Act and will remain eligible for deduction as qualified performance-based compensation. To the extent available, we intend to continue to treat “qualified performance-based compensation” that is grandfathered under the Tax Act as deductible compensation. We have not yet completed our evaluation of our existing compensation arrangements to determine whether any amounts payable to our Section 162(m) covered employees may continue to constitute qualified performance-based compensation under Section 162(m) and qualify under the grandfather provision. Therefore, we have not made any adjustments or estimates related to any potential tax liabilities in our financial statements related to the amendments to Section 162(m). Valuation allowances: The Company must assess whether valuation allowances assessments are affected by various aspects of the Tax Act (e.g., GILTI inclusions and new categories of FTCs). Since, as discussed herein, the Company has recorded no amounts related to certain portions of the Tax Act, any corresponding determination of the need for or change in a valuation allowance has not been completed and no changes to valuation allowances as a result of the Tax Act have been recorded. At December 31, 2017 and 2016, the tax effects of significant temporary differences representing deferred tax assets and liabilities were as follows: (In thousands) 2017 2016 Deferred Tax Liabilities: Depreciation $ (51,244 ) $ (75,973 ) Unrealized foreign exchange loss (734 ) (631 ) Other (2,066 ) (2,756 ) $ (54,044 ) $ (79,360 ) Deferred Tax Assets: Pensions $ 7,884 $ 12,077 Deferred revenue 232 940 Other accruals and reserves 13,660 20,590 Inventories 1,182 1,815 Legal and environmental accruals 7,243 11,503 Deferred compensation 15,402 24,485 Bad debt and rebate reserves 2,865 4,195 Non-U.S. subsidiaries net operating loss carryforwards 2,657 1,201 Tax credit carryforwards 1,851 1,599 $ 52,976 $ 78,405 Valuation Allowance $ (2,255 ) $ (1,815 ) Net Deferred Tax Liabilities $ (3,323 ) $ (2,770 ) Reconciliation to Consolidated Balance Sheet: Non-current deferred tax assets (in other non-current assets) 7,639 9,727 Non-current deferred tax liabilities (10,962 ) (12,497 ) Net Deferred Tax (Liabilities) Assets $ (3,323 ) $ (2,770 ) Earnings generated by a foreign subsidiary are presumed to ultimately be transferred to the parent company. Therefore, the establishment of deferred taxes may be required with respect to the excess of the investment value for financial reporting over the tax basis of investments in those foreign subsidiaries (also referred to as book-over-tax outside basis differences). A company may overcome this presumption and forgo recording a deferred tax liability in its financial statements if it can assert that management has the intent and ability to indefinitely reinvest the earnings of its foreign subsidiaries. Prior to the year ended December 31, 2017, the Company has not provided deferred U.S., foreign or local income taxes on the book-over-tax outside basis differences of its foreign subsidiaries because such excess has been considered to be indefinitely reinvested in the local country businesses. As discussed above, the Company has recorded $19.4 million in income tax expense, representing U.S. federal and state taxes expected to be incurred pursuant to the deemed repatriation of its foreign subsidiary earnings under the Tax Act in its consolidated statement of operations for the year ended December 31, 2017. Pursuant to the Tax Act, the Company now has the ability to repatriate to the U.S. parent the foreign cash associated with these foreign earnings as these earnings have already been subject to U.S. federal taxes. This cash may, however, be subject to foreign income and/or local country taxes if repatriated to the U.S. In addition, repatriation of some foreign cash balances may be further restricted by local laws. The Company is currently analyzing its foreign capital structure in order to determine the amount of cash at its foreign subsidiaries that can be repatriated to the U.S. with minimal additional taxes. This evaluation requires judgment about the future operating and liquidity needs of the Company and its foreign subsidiaries. Until such time as the Company completes this analysis, the Company maintains its assertion of indefinite reinvestment in its foreign earnings. The Company has non-U.S. tax loss carryforwards of $10,352,000 (pretax) as of December 31, 2017, and $4,655,000 as of December 31, 2016, that are available for use by the Company between 2018 and 2037. The Company has tax credit carryforwards of $1,851,000 as of December 31, 2017, and $1,599,000 as of December 31, 2016 that are available for use by the Company between 2018 and 2027. At December 31, 2017, the Company had valuation allowances of $2,255,000, which were primarily attributable to deferred tax assets in China, India, the Philippines and Singapore. The realization of deferred tax assets is dependent on the generation of sufficient taxable income in the appropriate tax jurisdictions. The Company believes that it is more likely than not that the related deferred tax assets will not be realized. As of December 31, 2017 and 2016, unrecognized tax benefits totaled $1,927,000 and $1,931,000, respectively. The amount of unrecognized tax benefits that, if recognized, would favorably affect the Company’s effective income tax rate in any future periods, net of the federal benefit on state issues, was approximately $1,917,000, $1,921,000 and $1,948,000 at December 31, 2017, 2016 and 2015, respectively. The Company believes it is reasonably possible that the amount of unrecognized tax benefits related to its current uncertain tax positions could decrease by up to $1,780,000 over the next 12 months. The Company recognizes accrued interest and penalties related to unrecognized tax benefits as income tax expense. In 2017, the Company recognized net interest and penalty expense of $3,000 compared to $9,000 of net interest and penalty expense in 2016 and $6,000 of net interest and penalty income in 2015. At December 31, 2017 the liability for interest and penalties was $56,000 compared to $53,000 at December 31, 2016. The Company files income tax returns in the U.S. federal jurisdiction and various states and foreign jurisdictions. The Company is not subject to U.S. federal income tax examinations by tax authorities for years before 2011. In addition, 2013 is no longer subject to U.S. federal income tax examinations. Some foreign jurisdictions and various U.S. states jurisdictions may be subject to examination back to 2011. During 2016, the Internal Revenue Service started its audit of the 2011 and 2012 tax years. As of December 31, 2017, these audits were still open and the Company had not been notified of any significant proposed adjustments. Below are reconciliations of the January 1 and December 31 balances of unrecognized tax benefits for 2017, 2016 and 2015: (In thousands) 2017 2016 2015 Unrecognized tax benefits, opening balance $ 1,931 $ 1,958 $ 464 Gross increases – tax positions in prior period — — 1,526 Gross increases – current period tax positions 20 35 29 Foreign currency translation 69 (43 ) (37 ) Lapse of statute of limitations (93 ) (19 ) (24 ) Unrecognized tax benefits, ending balance $ 1,927 $ 1,931 $ 1,958

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	10. Stockholders’ Equity At December 31, 2017 and 2016, treasury stock consisted of 3,561,509 shares and 3,470,084 shares of common stock, respectively. During 2017, 57,963 shares of Company common stock were purchased in the open market and 18,827 shares of Company common stock were purchased from Company Retirement Plans. In addition, 22,598

Stock-based Compensation

Stock-based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	11. Stock-based Compensation On December 31, 2017, the Company had stock options and stock awards outstanding under its 2006 Incentive Compensation Plan (2006 Plan) and stock options, stock awards and SARs under its 2011 Incentive Compensation Plan (2011 Plan). Stock options, stock awards and SARs are currently granted to Company executives and other key employees. No further options or awards may be granted under the 2006 Plan. The 2011 Plan authorized the award of 2,600,000 shares of the Company’s common stock for stock options, SARs and stock awards. At December 31, 2017, there were 945,161 shares available for grant under the 2011 Plan. Compensation expense recorded in the consolidated statements of income for all plans was $7,151,000, $12,618,000, and $4,374,000 The total income tax benefit recognized in the income statement for share-based compensation arrangements was $2,980,124, $4,761,000, and $1,654,000 Stock Options Under all plans, stock option awards are granted with an exercise price equal to the market price of the Company’s stock at the date of grant. The market price is defined and calculated as the average of the opening and closing prices for Company common stock on the grant date as reported in the New York Stock Exchange – Composite Transactions. Stock option awards granted prior to 2017 cliff vest after two years. Stock options granted in 2017 have a three-year graded vesting feature, with one-third of the awards vesting each year. The Company has elected the straight-line method of expense attribution for the stock options with graded vesting feature. These options have For the Years Ended December 31 2017 2016 2015 Expected dividend yield 1.39% 1.45% 1.53% Expected volatility 30.01% 35.62% 40.32% Expected term 7.2 years 7.3 years 7.3 years Risk-free interest rate 2.22% 1.52% 1.96% A summary of stock option activity for the year ended December 31, 2017 is presented below: Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term Aggregate Intrinsic ($000) Options Outstanding at January 1, 2017 436,126 $ 42.99 Granted 71,434 78.56 Exercised (104,277 ) 32.32 Forfeited (11,478 ) 50.78 Outstanding at December 31, 2017 391,805 52.09 6.33 $ 10,532 Vested or expected to vest at December 31, 2017 384,777 51.95 6.29 10,396 Exercisable at December 31, 2017 230,118 47.62 4.77 7,214 The weighted-average grant-date fair values of options awarded during the years ended December 31, 2017, 2016 and 2015, were $24.49, $14.70, and $15.59, respectively. The total intrinsic values of options exercised during the years ended December 31, 2017, 2016, and 2015 were $5,232,000, $6,620,000, and $1,426,000, respectively. As of December 31, 2017, the total unrecognized compensation cost for unvested stock options was $1,179,000. That cost is expected to be recognized over a weighted-average period of 2.0 years. Cash received from stock option exercises under the Company’s stock option plans for the years ended December 31, 2017, 2016, and 2015 was $3,370,000, $4,017,000, and $777,000 , respectively. The actual tax benefit realized for the tax deductions from stock option exercises totaled $1,455,000, $1,899,000, and $351,000 Stock Awards In 2015, 2016, and 2017, the Company granted stock awards under the 2011 Plan. Most Company stock awards are granted in the form of performance awards. The performance stock awards vest only upon the Company’s achievement of certain Board of Directors approved levels of financial performance by the end of specified measurement periods. The number of Company shares of common stock ultimately distributed, if any, is contingent upon the Company’s actual financial performance attained by the end of the measurement period relative to the Board of Directors approved targets. The fair value of performance stock awards equals the grant-date market price of the Company’s common stock, discounted for the estimated amount of dividends that would not be received during the measurement period. Compensation expense is recorded each reporting period based on the probable number of awards that will ultimately vest given the projected level of financial performance. If at the end of the measurement period the performance objectives are not met, no compensation cost is recognized and any compensation expense recorded in prior periods is reversed. Periodically, the Company also grants stock awards that have no performance conditions associated with their vesting. These stock awards vest based on the service time established for the given grant. A summary of stock award activity for the year ended December 31, 2017, is presented below: Shares Weighted-Average Grant Fair Value Stock Awards Unvested at January 1, 2017 256,766 $ 40.74 Granted 40,171 75.94 Vested (113,738 ) 39.54 Forfeited (14,166 ) 45.93 Unvested at December 31, 2017 169,033 The weighted-average grant-date fair values of stock awards granted during the years ended December 31, 2017, 2016 and 2015, were $75.94, $41.81, and $39.11 SARs At December 31, 2017, the Company had both cash-settled and Company stock-settled SARs outstanding. SARs granted prior to 2015 are cash-settled, and SARs granted after 2014 are stock-settled. SARs granted prior to 2017 cliff vest after two years. SARs granted in 2017 have a three-year graded vesting feature, with one-third of the awards vesting each year. The Company has elected the straight-line method of expense attribution for the SARs with graded vesting feature. All SARs The following is a summary of SARs activity for the year ended December 31, 2017: Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term Aggregate Intrinsic Value ($000) SARs Outstanding at January 1, 2017 553,582 $ 47.81 Granted 148,723 78.73 Exercised (73,739 ) 44.67 Forfeited (11,916 ) 68.95 Outstanding at December 31, 2017 616,650 55.23 7.46 $ 14,640 The weighted-average grant-date fair values of SARs granted during the years 2017, 2016 and 2015 were $24.90, $14.69, and $15.60 As of December 31, 2017 and 2016, the liability for cash-settled SARs recorded on the consolidated balance sheet (non-current liabilities) was $4,760,000 and $5,832,000, respectively. At December 31, 2017, there was $2,398,000 of total unrecognized compensation cost related to all unvested SARs. That cost is to be recognized over a weighted-average period of 2.0 years. In general, it is the Company’s policy to issue new shares of its common stock upon the exercise of stock options and stock-settled SARs or the vesting of stock awards.

Deferred Compensation

Deferred Compensation	12 Months Ended
	Dec. 31, 2017
Compensation Related Costs [Abstract]
Deferred Compensation	12. Deferred Compensation The Company sponsors deferred compensation plans that allow management employees to defer receipt of their annual bonuses and outside directors to defer receipt of their fees until retirement, departure from the Company or as otherwise elected. Compensation expense and the related deferred compensation obligation are recorded when the underlying compensation is earned. Over time, the deferred obligation may increase or decrease based on the performance results of investment options chosen by the plan participants. The investment options include Company common stock and a limited selection of mutual funds. The Company maintains sufficient shares of treasury stock to cover the equivalent number of shares that result from participants elections of the Company common stock investment option. As a result, the Company must periodically purchase its common shares in the open market or in private transactions. The Company purchases shares of the applicable mutual funds to fund the portion of its deferred compensation liabilities tied to such investments. Some plan distributions may be made in cash or Company common stock at the option of the participant. Other plan distributions can only be made in Company common stock. For deferred compensation obligations that may be settled in cash or Company common stock at the option of the participant, the Company must record appreciation in the market values of the investment choices made by participants as additional compensation expense. Conversely, declines in the market values of the investment choices reduce compensation expense. Increases and decreases of compensation expense that result from fluctuations in the underlying investments are recorded as part of operating expenses in the consolidated statements of income. The additional compensation expense resulting from the changes in the market values and earnings of the selected investment options was $4,857,000 $16,805,000 and $6,500,000 expense in 2017, 2016 and 2015, respectively. The decrease in expense between 2017 and 2016 was attributable to a decrease in the market value of the Company’s common stock and an increase in income from investments other than in Company’s common stock. Between 2016 and 2015, the price of the Company’s common stock significantly increased resulting in higher deferred compensation. The obligations that must be settled only in Company common stock are treated as equity instruments; therefore, fluctuations in the market price of the underlying Company stock do not affect earnings. The Company’s deferred compensation liability was $58,915,000

Postretirement Benefit Plans

Postretirement Benefit Plans	12 Months Ended
	Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
Postretirement Benefit Plans	13. Postretirement Benefit Plans Defined Benefit Plans The Company sponsors various funded qualified and unfunded non-qualified defined benefit pension plans, the most significant of which cover employees in the U.S. and U.K. locations. The various U.S. defined benefit pension plans were amended in 2005-2008 to freeze the plans by stopping the accrual of service benefits. The U.K. defined benefit pension plan was frozen in 2006. Benefits earned through the freeze dates are available to participants when they retire, in accordance with the terms of the plans. The Company established defined contribution plans to replace the frozen defined benefit pension plans. Obligations and Funded Status at December 31 United States United Kingdom (In thousands) 2017 2016 2017 2016 Change in benefit obligation Benefit obligation at beginning of year $ 162,727 $ 160,789 $ 22,034 $ 19,950 Interest cost 6,651 6,934 592 733 Actuarial (gain) loss 9,109 1,538 (156 ) 5,614 Benefits paid (7,129 ) (6,534 ) (516 ) (513 ) Foreign exchange impact — — 2,094 (3,750 ) Benefit obligation at end of year $ 171,358 $ 162,727 $ 24,048 $ 22,034 United States United Kingdom (In thousands) 2017 2016 2017 2016 Change in plan assets Fair value of plan assets at beginning of year $ 137,092 $ 121,835 $ 20,336 $ 21,425 Actual return on plan assets 15,533 21,612 1,957 2,758 Employer contributions 2,412 179 365 378 Benefits paid (7,129 ) (6,534 ) (516 ) (513 ) Foreign exchange impact — — 2,026 (3,712 ) Fair value of plan assets at end of year $ 147,908 $ 137,092 $ 24,168 $ 20,336 Over (Under) funded status at end of year $ (23,450 ) $ (25,635 ) $ 120 $ (1,698 ) The amounts recognized in the consolidated balance sheets at December 31 consisted of United States United Kingdom (In thousands) 2017 2016 2017 2016 Non-current asset $ — $ — $ 120 — Current liability (302 ) (166 ) — — Non-current liability (23,148 ) (25,469 ) — (1,698 ) Net amount recognized $ (23,450 ) $ (25,635 ) $ 120 $ (1,698 ) The amounts recognized in accumulated other comprehensive income at December 31 consisted of United States United Kingdom (In thousands) 2017 2016 2017 2016 Net actuarial loss $ 39,801 $ 40,022 $ 5,743 $ 7,443 Below is information for pension plans with projected benefit obligations in excess of plan assets at December 31: United States United Kingdom (In thousands) 2017 2016 2017 2016 Projected benefit obligation $ 171,358 $ 162,727 $ — $ 22,034 Accumulated benefit obligation 171,358 162,727 — 22,034 Fair value of plan assets 147,908 137,092 — 20,336 Components of Net Periodic Benefit Cost and Other Amounts Recognized in Other Comprehensive Income Net periodic benefit costs for the years ended December 31, 2017, 2016 and 2015, were as follows: United States United Kingdom (In thousands) 2017 2016 2015 2017 2016 2015 Interest cost $ 6,651 $ 6,934 $ 6,815 $ 592 $ 733 $ 789 Expected return on plan assets (9,288 ) (9,012 ) (9,579 ) (797 ) (900 ) (1,054 ) Amortization of net actuarial loss 3,085 3,386 4,534 382 77 179 Net periodic benefit cost $ 448 $ 1,308 $ 1,770 $ 177 $ (90 ) $ (86 ) Other changes in plan assets and benefit obligations recognized in other comprehensive income for the years ended December 31, 2017, 2016 and 2015, were as follows: United States United Kingdom (In thousands) 2017 2016 2015 2017 2016 2015 Net actuarial (gain) loss $ 2,864 $ (11,062 ) $ (1,110 ) $ (1,318 ) $ 3,756 $ (781 ) Amortization of net actuarial loss (3,085 ) (3,386 ) (4,534 ) (382 ) (77 ) (179 ) Total recognized in other comprehensive income $ (221 ) $ (14,448 ) $ (5,644 ) $ (1,700 ) $ 3,679 $ (960 ) Total recognized in net periodic benefit cost and other comprehensive income $ 227 $ (13,140 ) $ (3,874 ) $ (1,523 ) $ 3,589 $ (1,046 ) The estimated amounts that will be reclassified from accumulated other comprehensive income into net periodic benefit cost in 2018 are as follows: (In thousands) United States United Kingdom Net actuarial loss $ 3,746 $ 222 Estimated Future Benefit Payments (In thousands) United States United Kingdom 2018 $ 7,560 $ 504 2019 7,956 511 2020 8,438 516 2021 8,973 539 2022 9,448 585 2023-2027 51,168 3,548 Assumptions The weighted-average assumptions used to determine benefit obligations at December 31 were as follows: United States United Kingdom 2017 2016 2017 2016 Discount rate 3.67 % 4.17 % 2.40 % 2.60 % The weighted-average assumptions used to determine net periodic benefit costs for years ended December 31 were as follows: United States United Kingdom 2017 2016 2015 2017 2016 2015 Discount rate 4.17 % 4.39 % 4.09 % 2.60 % 4.00 % 3.50 % Expected long-term return on plan assets 7.00 % 7.00 % 7.50 % 3.77 % 4.59 % 4.66 % In addition to the above assumptions, the Company uses a market-related value of assets approach to calculate the expected return on plan assets component of U.S. net periodic benefit cost. The market-related value equals the fair value of plan assets with five-year smoothing of asset gains or losses. Asset gains are subtracted or losses added in the following way: 80 percent of the prior year’s gain or loss; 60 percent of the second preceding year’s gain or loss; 40 percent of the third preceding year’s gain or loss; and 20 percent of the fourth preceding year’s gain or loss. Gains or losses for the year are calculated as the difference between the expected fair value of assets and the actual fair value of assets. Investment Strategies and Policies U.S. Plans Plan assets are predominantly invested using active investment strategies, as compared to passive or index investing. An investment management firm hires and monitors underlying investment management firms for each asset category. Equity managers within each category cover a range of investment styles and approaches, including both active and passive, and are combined in a way that controls for capitalization, style biases, and country exposure versus benchmark indexes, while active managers focus primarily on stock selection to improve returns. Fixed income managers seek to reduce the volatility of the plan’s funded status by matching the duration with the plan’s liability while seeking to improve returns through security selection, sector allocation and yield curve management. Real estate (REIT) exposure is now categorized within mid cap equity and uses public core real estate strategies, which provide stable and high levels of current income and enhanced core strategies, which seek slightly higher returns by emphasizing appreciation. Risk is controlled through diversification among multiple asset categories, managers, styles, and securities. The investment management firm recommends asset allocations based on the time horizon available for investment, the nature of the plan cash flows and liabilities and other factors that affect risk tolerance. The asset allocation targets are approved by the Company’s Plan Committee. Risk is further controlled both at the manager and asset category level by assigning targets for risk versus investment returns. Allowable investment categories include: Equities: Common stocks of large, medium, and small companies, including both U.S. and non-U.S. based companies. The long-term target allocation for equities, excluding Company stock, is 50 Fixed Income (Debt): Bonds or notes issued or guaranteed by the U.S. government, and to a lesser extent, by non-U.S. governments, or by their agencies or branches, mortgage-backed securities, including collateralized mortgage obligations, corporate bonds, municipal bonds and dollar-denominated debt securities issued in the U.S. by non-U.S. banks and corporations. A small percentage of the fixed income assets may be in debt securities that are below investment grade. The target allocation for fixed income is 30 percent. Real Estate: Public real estate funds using office, apartment, industrial, retail and other property types. In prior years Real Estate investments were reflected as a separate line item within the Mutual Funds category. Effective 2017, the majority of Real Estate assets have been removed from this category and are currently being captured within the Equities assets category. This change was made by the Global Industry Classification Standard (GICS) to better reflect the equity security features of Real Estate Investment Trusts (REITs). Commodities: In previous years, the retirement plans invested in Commodity funds that match the index using commodity-linked derivative instruments while seeking to enhance overall returns through the use of fixed income securities. The retirement plan exited commodities in 2017 because of their high correlation to long term fixed income - they no longer provided the diversification benefit to the long term asset allocation optimization. Employer Securities: The retirement plans also hold shares of the Company’s common stock, which are purchased or sold by the trustee from time to time, as directed by the Plan Committee. At the direction of the Plan Committee, the plans sold 40,837 common shares to the Company’s ESOP trust on February 21, 2017, 18,827 In addition to these primary investment types, excess cash may be invested in futures in order to efficiently achieve more fully invested portfolio positions. Otherwise, a small number of investment managers make limited use of derivatives, including futures contracts, options on futures and interest rate swaps in place of direct investment in securities to efficiently achieve equivalent market positions. Derivatives are not used to leverage portfolios. U.K. Plan The objective of the U.K. defined benefit pension fund investment strategy is to maximize the long-term rate of return on plan assets within a medium level of risk in order to minimize the cost of providing pension benefits. To that end, the plan assets are invested in an actively managed pooled fund of funds that diversifies its holdings among equity securities, debt securities, property and cash. Essentially, the plan is to hold equity instruments to back the benefits of participants yet to retire and bonds and cash to back current pensioners. Although there are no formal target allocations for the plan assets, the fund will generally be heavily invested in equity securities. Equity securities are selected from U.K., European, U.S. and emerging market companies. Bonds include U.K. and other countries’ government notes and corporate debt of U.K and non-U.K. companies. There are no specific prohibited investments, but the current managed fund will not allocate assets to derivatives or other financial hedging instruments. Plan trustees meet regularly with the fund manager to assess the fund’s performance and to reassess investment strategy. At December 31, 2017, the pension asset allocation was 58 percent equities, 29 percent fixed income, seven percent insurance contracts, three percent real estate and three Included in plan assets are insurance contracts purchased by the plan trustees to provide pension payments for specific retirees. In past years, at the time a plan participant retired, the plan trustee would periodically purchase insurance contracts to cover the future payments due the retiree. This practice is no longer followed. The contracts are revocable, and the related plan obligations are not considered settled. Therefore, the plan assets and obligations include the insured amounts. Plan Assets U.S. Plans The Company’s asset allocations for its U.S. pension plans at December 31, 2017 and 2016, by asset category, were as follows: December 31, 2017 (In thousands) Level 1 Level 2 Level 3 Total Cash and Cash Equivalents $ 4,903 $ — $ — $ 4,903 Equity Securities U.S. Equities 37,753 — — 37,753 Non-U.S. Equities 31,581 47 — 31,628 Employer Securities 30,197 — — 30,197 Total Equities 99,531 47 — 99,578 Fixed Income Securities U.S. Corporate Bonds — 28,744 — 28,744 U.S. Government and Agency Bonds 5,545 1,045 — 6,590 Other Bonds — 8,093 — 8,093 Total Fixed Income 5,545 37,882 — 43,427 Total $ 109,979 $ 37,929 $ — $ 147,908 December 31, 2016 (In thousands) Level 1 Level 2 Level 3 Total Cash and Cash Equivalents $ 3,633 $ 275 $ — $ 3,908 Equity Securities U.S. Equities 29,390 — — 29,390 Non-U.S. Equities 14,637 — — 14,637 Employer Securities 36,018 — — 36,018 Total Equities 80,045 — — 80,045 Fixed Income Securities U.S. Corporate Bonds — 28,278 — 28,278 U.S. Government and Agency Bonds 8,309 971 — 9,280 Other Bonds — 7,696 — 7,696 Total Fixed Income 8,309 36,945 — 45,254 Mutual Funds Real Estate 5,362 — — 5,362 Commodities 2,523 — — 2,523 Other — — — — Total Mutual Funds 7,885 — — 7,885 Total $ 99,872 $ 37,220 $ — $ 137,092 Plan Asset Valuation Methodology Following is a description of the valuation methodologies used for plan assets measured at fair value. Individual equity securities, including employer securities, are valued by Standard & Poor’s Securities Evaluations as determined by quoted market prices on the New York Stock Exchange or other active markets. Both market pricing and future cash flow analysis may be used in the pricing process as follows: Level 1 – Equities represent the largest asset category and are valued according to the exchange-quoted market prices of the underlying investments. Level 1 fixed income securities are U.S. government securities and are valued according to quoted prices from active markets. Level 2 – Fixed income investments without equivalent trading exchanges are valued primarily through a technique known as “future cash flow approach” which is based on what bondholders can reasonably expect to receive based upon an issuer’s current financial condition. Pricing analysts prepare cash-flow forecasts and utilize one or two pricing models to arrive at an evaluated price. Evaluated bid modeling includes factors such as the interest rate on the coupon, maturity, rating, cash flow projections and other factors. Level 3 – no investments held during 2017 or 2016 were categorized as Level 3. U.K. Plan The Company’s asset allocations for its U.K. pension plans at December 31, 2017 and 2016, by asset category, were as follows: December 31, 2017 (In thousands) Level 1 Level 2 Level 3 Total Cash $ 745 $ — $ — $ 745 Equity Securities Pooled Pension Funds — 14,127 — 14,127 Fixed Income Pooled Pension Funds — 6,952 — 6,952 Real Estate Pooled Pension Funds — 646 — 646 Insurance Contracts — — 1,698 1,698 Total $ 745 $ 21,725 $ 1,698 $ 24,168 December 31, 2016 (In thousands) Level 1 Level 2 Level 3 Total Cash $ 243 $ — $ — $ 243 Equity Securities Pooled Pension Funds — 11,760 — 11,760 Fixed Income Pooled Pension Funds — 6,015 — 6,015 Real Estate Pooled Pension Funds — 559 — 559 Insurance Contracts — — 1,759 1,759 Total $ 243 $ 18,334 $ 1,759 $ 20,336 Units of each of the pooled funds are valued by the trustee based on quoted market prices of the underlying investments (the underlying assets are either exchange traded or have readily available markets). Fair value changes within asset categories for which fair value measurements use significant unobservable inputs (Level 3) were as follows during 2016 and 2017: (In thousands) Insurance Fair value, December 31, 2015 $ 1,969 Sale proceeds (benefit payments) (144 ) Change in unrealized gain 265 Foreign exchange impact (331 ) Fair value, December 31, 2016 $ 1,759 Sale proceeds (benefit payments) (134 ) Change in unrealized gain (84 ) Foreign exchange impact 157 Fair value, December 31, 2017 $ 1,698 Long-term Rate of Return for Plan Assets U.S. Plans The overall expected long-term rate of return on assets of 7.00 percent that was used to develop the 2017 pension expense is based on plan asset allocation, capital markets forecasts and expected benefits of active investment management. For fixed income, the expected return is 4.69 percent. This assumption includes the yield on the five-year zero-coupon U.S. Treasury bond as the base rate along with historical data from the U.S. Treasury yield curve. For equities, the expected return is 6.31 percent for U.S. and international equities. This return is based on a blended average of three different statistical models that each incorporates multiple factors including, for example, inflation, Gross Domestic Product and the Fed Funds Target Rate. The overall investment return forecast reflects the target allocations and the capital markets forecasts for each asset category, plus a premium for active asset management expected over the long-term. U.K. Plan The overall expected long-term return on plan assets is a weighted-average of the expected long-term returns for equity securities, debt securities and other assets. The redemption yield at the measurement date on U.K. government fixed interest bonds and the yield on corporate bonds are used as proxies for the return on the debt portfolio. The returns for equities and property are estimated as a premium of 3.0 percent added to the risk-free rate. Cash is assumed to have a long-term return of 4.0 percent. Other Defined Benefit Plans The Company maintains funded and unfunded defined benefit plans in other foreign locations. The liabilities and expenses associated with these plans, individually and collectively, are not material to the Company’s consolidated financial statements. Discount rates for these plans are determined based on local interest rates and plan participant data. Cash Flows As a result of pension funding relief included in the Highway and Transportation Funding Act of 2014, the Company does not expect to make any 2018 contributions to the funded U.S. qualified defined benefit plans. The Company expects to contribute $302,000 in 2018 to the unfunded non-qualified U.S. pension plans. The Company expects to contribute $461,000 to the U.K. defined benefit plan in 2018. Defined Contribution Plans The Company sponsors retirement savings defined contribution retirement plans that cover eligible U.S. and U.K. employees. The Company’s U.S retirement plans include two qualified plans, one of which is a 401(k) plan and one of which is an employee stock ownership plan, and one non-qualified supplemental executive plan. Historically, the Company has made profit sharing contributions into the qualified retirement plans for its U.S. employees. Profit sharing contributions were determined each year using a formula that was applied to Company earnings. The contributions, which were made partly in cash paid to the 401(k) plan and partly in Company common stock, are allocated to participant accounts on the basis of participant base earnings. Defined contribution expenses for the Company’s qualified defined contribution plans were as follows: (In thousands) 2017 2016 2015 Retirement contributions $ 4,998 $ 4,902 $ 4,644 Profit sharing contributions 7,002 6,230 4,972 Total $ 12,000 $ 11,132 $ 9,616 The Company has a rabbi trust to fund the obligations of its non-qualified supplemental executive defined contribution plans (supplemental plans). The trust comprises various mutual fund investments selected by the participants of the supplemental plans. In accordance with the accounting guidance for rabbi trust arrangements, the assets of the trust and the obligations of the supplemental plans are reported on the Company’s consolidated balance sheet. The Company elected the fair value option for the mutual fund investment assets so that offsetting changes in the mutual fund values and defined contribution plan obligations would be recorded in earnings in the same period. Therefore, the mutual funds are reported at fair value with any subsequent changes in fair value recorded in the income statement. The supplemental plan liabilities increase (i.e., supplemental plan expense is recognized) when the value of the trust assets appreciates and decrease (i.e., supplemental plan income is recognized) when the value of the trust assets declines. At December 31, 2017 and 2016, the trust asset balances were $1,587,000 and $1,692,000, respectively, and the supplemental plan liability balances were $1,661,000 and $1,767,000, respectively. The differences between the trust asset balances and the supplemental liability balances were due to estimated liabilities that were not funded until after the end of the year when the actual liabilities were determined. In addition to the contributions described above, certain foreign locations are required by law to make profit sharing contributions to employees based on statutory formulas. For the years ended December 31, 2017, 2016 and 2015, the Company recognized $398,000, $290,000 and $1,375,000, respectively, of statutory profit sharing expense.

Accrued Liabilities

Accrued Liabilities	12 Months Ended
	Dec. 31, 2017
Payables And Accruals [Abstract]
Accrued Liabilities	14. Accrued Liabilities The composition of accrued liabilities was as follows: December 31 (In thousands) 2017 2016 Accrued payroll and benefits $ 58,877 $ 66,575 Accrued customer rebates 16,729 18,553 Other accrued liabilities 17,170 25,667 Total accrued liabilities $ 92,776 $ 110,795

Other Non-Current Liabilities

Other Non-Current Liabilities	12 Months Ended
	Dec. 31, 2017
Other Liabilities Disclosure [Abstract]
Other Non-Current Liabilities	15. Other Non-Current Liabilities The composition of other non-current liabilities was as follows: December 31 (In thousands) 2017 2016 Deferred revenue $ 1,539 $ 1,863 Environmental and legal matters 21,888 22,703 Deferred compensation liability 51,890 53,133 Pension liability 25,632 29,494 Other non-current liabilities 29,484 12,160 Total other non-current liabilities $ 130,433 $ 119,353

Contingencies

Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Contingencies	16. Contingencies There are a variety of legal proceedings pending or threatened against the Company. Some of these proceedings may result in fines, penalties, judgments or costs being assessed against the Company at some future time. The Company’s operations are subject to extensive local, state and federal regulations, including the U.S. Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA) and the Superfund amendments of 1986 (Superfund) as well as similar regulations in other countries where the Company operates. Over the years, the Company has received requests for information related to or has been named by government authorities as a PRP at a number of waste disposal and manufacturing sites where cleanup costs have been or may be incurred under CERCLA and similar state statutes. In addition, damages are being claimed against the Company in general liability actions for alleged personal injury or property damage in the case of some disposal and plant sites. The Company believes that it has made adequate provisions for the costs it may incur with respect to these sites. As of December 31, 2017, the Company estimated a range of possible environmental and legal losses of $24.2 For certain sites, the Company has responded to information requests made by federal, state or local government agencies but has received no response confirming or denying the Company’s stated positions. As such, estimates of the total costs, or range of possible costs, of remediation, if any, or the Company’s share of such costs, if any, cannot be determined with respect to these sites. Consequently, the Company is unable to predict the effect thereof on the Company’s financial position, cash flows and results of operations. Given the information available, management believes the Company has no liability at these sites. However, in the event of one or more adverse determinations with respect to such sites in any annual or interim period, the effect on the Company’s cash flows and results of operations for those periods could be material. Based upon the Company’s present knowledge with respect to its involvement at these sites, the possibility of other viable entities’ responsibilities for cleanup, and the extended period over which any costs would be incurred, the Company believes that these matters, individually and in the aggregate, will not have a material effect on the Company’s financial position. However, in the event of one or more adverse determinations with respect to such sites in any annual or interim period, the effect on the Company’s cash flows and results of operations for those periods could be material. Following are summaries of the major contingencies at December 31, 2017: Maywood, New Jersey Site The Company’s property in Maywood, New Jersey and property formerly owned by the Company adjacent to its current site and other nearby properties (Maywood site) were listed on the National Priorities List in September 1993 pursuant to the provisions of CERCLA because of certain alleged chemical contamination. Pursuant to an Administrative Order on Consent entered into between USEPA and the Company for property formerly owned by the Company, and the issuance of an order by USEPA to the Company for property currently owned by the Company, the Company has completed various Remedial Investigation Feasibility Studies (RI/FS), and on September 24, 2014, USEPA issued its Record of Decision (ROD) for chemically-contaminated soil. USEPA has not yet issued a ROD for chemically-contaminated groundwater for Maywood site. Based on the most current information available, the Company believes its recorded liability represents its best estimate of the cost of remediation for the Maywood site. The best estimate of the cost of remediation for the Maywood site could change as the Company continues to hold discussions with USEPA, as the design of the remedial action progresses, if a groundwater ROD is issued or if other PRPs are identified. The ultimate amount for which the Company is liable could differ from the Company’s current recorded liability. In April 2015, the Company entered into an Administrative Settlement Agreement and Administrative Order on Consent with USEPA which requires payment of certain costs and performance of certain investigative and design work for chemically-contaminated soil. Based on the Company’s review and analysis of this order, no changes to the Company’s current recorded liability for claims associated with soil remediation of chemical contamination were required. In addition, under the terms of a settlement agreement reached on November 12, 2004, the United States Department of Justice and the Company agreed to fulfill the terms of a Cooperative Agreement reached in 1985 under which the United States will take title to and responsibility for radioactive waste removal at the Maywood site, including past and future remediation costs incurred by the United States. As such, the Company recorded no liability related to this settlement agreement. D’Imperio Property Site During the mid-1970’s, Jerome Lightman and the Lightman Drum Company disposed of hazardous substances at several sites in New Jersey. The Company was named as a PRP in a lawsuit in the U.S. District court for the district of New Jersey that involved the D’Imperio Property Site located in New Jersey. In 2016, the PRPs were provided with updated remediation cost estimates which were considered in the Company’s determination of its range of estimated possible losses and liability balance. The changes in range of possible losses and liability balance were immaterial. Remediation work is continuing at this site. Based on current information, the Company believes that its recorded liability represents its best estimate of the cost of remediation for the D’Imperio site. Depending on the ultimate cost of the remediation at this site, the amount for which the Company is liable could differ from the current estimates. Wilmington Site The Company is currently contractually obligated to contribute to the response costs associated with the Company’s formerly-owned site in Wilmington, Massachusetts. Remediation at this site is being managed by its current owner to whom the Company sold the property in 1980. Under the agreement, once total site remediation costs exceed certain levels, the Company is obligated to contribute up to five percent of future response costs associated with this site with no limitation on the ultimate amount of contributions. The Company has paid the current owner $2.5 million for the Company’s portion of environmental response costs through December 31, 2017. The Company has recorded a liability for its portion of the estimated remediation costs for the site. Depending on the ultimate cost of the remediation at this site, the amount for which the Company is liable could differ from the current estimates. The Company and other prior owners also entered into an agreement in April 2004 waiving certain statute of limitations defenses for claims which may be filed by the Town of Wilmington, Massachusetts, in connection with this site. While the Company has denied any liability for any such claims, the Company agreed to this waiver while the parties continue to discuss the resolution of any potential claim which may be filed. Other U.S. Sites Through the regular environmental monitoring of its plant production sites, the Company discovered levels of chemical contamination that were above thresholds allowed by law at two of its U.S plants. The Company voluntarily reported its results to the applicable state environmental agencies. As a result, the Company is required to perform self-remediation of the affected areas. In the fourth quarter of 2016, the Company recognized a charge for the estimated cost of remediating the sites. The charge was not material to the Company’s results of operations. Based on current information, the Company believes that its recorded liability for the remediation is adequate. However, actual costs could differ from current estimates.

Segment Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Reporting	17. Segment Reporting The Company has three reportable segments: Surfactants, Polymers and Specialty Products. Each segment provides distinct products and requires separate management due to unique markets, technologies and production processes. Surfactants are used in a variety of consumer and industrial cleaning compounds as well as in agricultural products, lubricating ingredients, oil field chemicals and other specialized applications. Polymers are used primarily in plastics, building materials, refrigeration systems and CASE applications. Specialty Products are used in food, flavoring, nutritional supplement and pharmaceutical applications. The Company evaluates the performance of its segments and allocates resources based on operating income before interest expense, other income/expense items and income tax provision. The accounting policies of the reportable segments are the same as those described in the summary of significant accounting policies. The following is segment data for the three years ended December 31, 2017, 2016 and 2015: (In thousands) Surfactants Polymers Specialty Products Segment Totals 2017 Net sales $ 1,297,555 $ 546,634 $ 80,818 $ 1,925,007 Operating income 119,990 82,801 9,952 212,743 Assets 881,415 355,065 75,452 1,311,932 Capital expenditures 50,400 21,146 4,234 75,780 Depreciation and amortization expenses 49,102 22,998 5,019 77,119 2016 Net sales $ 1,181,563 $ 498,826 $ 85,777 $ 1,766,166 Operating income 99,796 96,788 10,698 207,282 Assets 831,324 301,890 75,483 1,208,697 Capital expenditures 64,121 31,890 4,194 100,205 Depreciation and amortization expenses 48,643 20,275 4,204 73,122 2015 Net sales $ 1,205,849 $ 491,488 $ 78,830 $ 1,776,167 Operating income 104,080 80,942 4,397 189,419 Assets 758,524 293,790 72,604 1,124,918 Capital expenditures 79,171 31,309 6,387 116,867 Depreciation and amortization expenses 42,122 19,541 3,659 65,322 Below are reconciliations of segment data to the consolidated financial statements: (In thousands) 2017 2016 2015 Operating income - segment totals $ 212,743 $ 207,282 $ 189,419 Business restructuring and asset impairments (a) (3,069 ) (7,064 ) — Unallocated corporate expenses (b) (63,514 ) (74,025 ) (66,629 ) Total operating income 146,160 126,193 122,790 Interest expense, net (11,444 ) (13,205 ) (14,533 ) Loss from equity in joint ventures — — (6,985 ) Other, net 4,521 828 1,584 Consolidated income before income taxes $ 139,237 $ 113,816 $ 102,856 Assets - segment totals $ 1,311,932 $ 1,208,697 $ 1,124,918 Unallocated corporate assets (c) 158,929 145,193 113,474 Consolidated assets $ 1,470,861 $ 1,353,890 $ 1,238,392 Capital expenditures - segment totals $ 75,780 $ 100,205 $ 116,867 Unallocated corporate expenditures 2,833 2,871 2,482 Consolidated capital expenditures $ 78,613 $ 103,076 $ 119,349 Depreciation and amortization expenses – segment totals $ 77,119 $ 73,122 $ 65,322 Unallocated corporate depreciation expenses 1,903 1,845 1,663 Consolidated depreciation and amortization expenses $ 79,022 $ 74,967 $ 66,985 (a) See Note 22 regarding business restructuring and asset impairment costs. (b) Unallocated corporate expenses primarily comprise corporate administrative expenses (e.g., corporate finance, legal, human resources, information systems, deferred compensation and environmental remediation) that are not included in segment operating income and not used to evaluate segment performance. (c) The changes in unallocated corporate assets between 2017, 2016 and 2015 were primarily attributable to changes in the balance of U.S. cash and cash equivalents, which are not allocated to segments. Below is certain Company-wide geographic data for the years ended December 31, 2017, 2016 and 2015: (In thousands) 2017 2016 2015 Net sales (a) United States $ 1,159,578 $ 1,076,259 $ 1,069,526 France 176,052 151,031 169,072 Poland 188,244 153,986 150,654 United Kingdom 99,069 86,458 89,757 Brazil 109,960 74,961 63,439 All other countries 192,104 223,471 233,719 Total $ 1,925,007 $ 1,766,166 $ 1,776,167 Long-lived assets (b) United States $ 420,342 $ 411,023 $ 387,744 Germany 29,116 27,475 30,268 Singapore 33,530 36,270 39,181 Brazil (c) 55,974 58,106 26,721 China 30,849 29,508 25,689 United Kingdom 21,657 20,309 22,943 All other countries 50,631 47,670 52,139 Total $ 642,099 $ 630,361 $ 584,685 (a) Net sales are attributed to countries based on the location of the Company facility making the sales. (b) Includes net property, plant and equipment, goodwill and other intangible assets. (c) The change between 2016 and 2015 was attributable to the acquisition described in Note 20.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	18. Earnings Per Share Below is the computation of basic and diluted earnings per share for the years ended December 31, 2017, 2016 and 2015. (In thousands, except per share amounts) 2017 2016 2015 Computation of Basic Earnings per Share Net income attributable to Stepan Company $ 91,578 $ 86,191 $ 75,968 Weighted-average number of shares outstanding 22,946 22,793 22,730 Basic earnings per share $ 3.99 $ 3.78 $ 3.34 Computation of Diluted Earnings per Share Net income attributable to Stepan Company $ 91,578 $ 86,191 $ 75,968 Weighted-average number of shares outstanding 22,946 22,793 22,730 Add weighted-average net shares from assumed exercise of options (under treasury share method) (a) 161 159 118 Add weighted-average net shares related to unvested stock awards (under treasury share method) 8 6 3 Add weighted-average net shares from assumed exercise of SARs (under treasury share method) 142 68 1 Add weighted-average contingently issuable net shares related to performance stock awards (under treasury share method) 120 68 6 Weighted-average shares applicable to diluted earnings 23,377 23,094 22,858 Diluted earnings per share $ 3.92 $ 3.73 $ 3.32 (a ) Options to purchase 18,630, 43,715 and 124,531 shares of common stock were not included in the computations of diluted earnings per share for the years ended December 31, 2017, 2016 and 2015, respectively. The options’ exercise prices were greater than the average market price for the common stock and the effect of the options on earnings per share would have been antidilutive.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	19. Accumulated Other Comprehensive Income (Loss) Below is the change in the Company’s accumulated other comprehensive income (loss) (AOCI) balance by component (net of income taxes) for the years ended December 31, 2017, 2016 and 2015: (In thousands) Foreign Currency Translation Adjustments Defined Benefit Pension Plan Adjustments Cash Flow Hedge Adjustments Total Balance at December 31, 2014 $ (42,914 ) $ (41,149 ) $ 118 $ (83,945 ) Other comprehensive income before reclassifications (45,423 ) 1,311 (49 ) (44,161 ) Amounts reclassified from AOCI — 3,013 5 3,018 Net current period other comprehensive income (45,423 ) 4,324 (44 ) (41,143 ) Balance at December 31, 2015 $ (88,337 ) $ (36,825 ) $ 74 $ (125,088 ) Other comprehensive income before reclassifications (8,438 ) 3,818 (19 ) (4,639 ) Amounts reclassified from AOCI — 2,217 45 2,262 Net current period other comprehensive income (8,438 ) 6,035 26 (2,377 ) Balance at December 31, 2016 $ (96,775 ) $ (30,790 ) $ 100 $ (127,465 ) Other comprehensive income before reclassifications 26,214 (582 ) — 25,632 Amounts reclassified from AOCI — 2,279 (9 ) 2,270 Net current period other comprehensive income 26,214 1,697 (9 ) 27,902 Balance at December 31, 2017 $ (70,561 ) $ (29,093 ) $ 91 $ (99,563 ) Amounts reclassified out of AOCI for the three years ended December 31, 2017, 2016 and 2015, is displayed below: Amounts Reclassified from AOCI (a) Affected Line Item in Consolidated (In thousands) 2017 2016 2015 Statements of Income Amortization of defined pension items: Prior service cost $ (14 ) $ (14 ) $ (17 ) Actuarial loss (3,509 ) (3,508 ) (4,757 ) $ (3,523 ) (3,522 ) (4,774 ) Total before tax (b) 1,244 1,305 1,761 Tax benefit $ (2,279 ) $ (2,217 ) $ (3,013 ) Net of tax Gains and losses on cash flow hedges: Interest rate contracts $ — $ (82 ) $ (22 ) Interest, net Foreign exchange contracts 9 9 9 Cost of sales 9 (73 ) (13 ) Total before tax 28 8 Tax benefit $ 9 $ (45 ) $ (5 ) Net of tax Total reclassifications for the period $ (2,270 ) $ (2,262 ) $ (3,018 ) Net of tax (a) Amounts in parentheses denote expense to statement of income. (b) This component of accumulated other comprehensive income is included in the computation of net periodic benefit cost (see Note 13 for details regarding net periodic benefit costs for the Company’s U.S. and U.K. defined benefit plans).

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions	20. Acquisitions 2017 Acquisition Agreement On June 13, 2017, the Company announced that it had reached an agreement with BASF Mexicana, S.A. DE C.V. (BASF) to acquire BASF’s production facility in Ecatepec, Mexico, and a portion of its related surfactants business. The facility, which is near Mexico City, has over 50,000 metric tons of capacity, 124,000 square feet of warehouse space, a laboratory and office space. The acquisition is currently expected to be completed in 2018, subject to normal closing conditions including necessary governmental consents. The acquisition supports the Company’s growth strategies in Latin America. The acquired facility and business will be included in the Company’s Surfactant segment. 2016 Business Acquisitions O n October 3, 2016, the Company’s subsidiary in Brazil acquired the commercial business of Tebras Tensoativos do Brasil Ltda. (Tebras) and the sulfonation production facility of PBC Industria Quimica Ltda. (PBC). The original purchase price of the acquisitions, including adjustments for working capital, was R$93,309,000 (approximately $29,075,000), of which R$70,000,000 (approximately $21,812,000) was paid in the fourth quarter of 2016 from cash on hand, R$9,000,000 (approximately $2,804,000) was deposited in escrow to cover certain potential losses as specified in the purchase agreement and R$14,309,000 (approximately $4,459,000) for working capital adjustments was unpaid at December 31, 2016 pending agreement on the adjustment amounts. (All U.S. dollar equivalents were calculated using the October 3, 2016 exchange rates.) In the first quarter of 2017, the Company settled on and paid the working capital adjustment amounts that were outstanding at December 31, 2016. The payment totaled R$13,925,000 (approximately $4,339,000), which made the adjusted purchase price of the acquisitions R$92,925,000 (approximately $28,955,000). As a result of the change in purchase price, the amount of the purchase price allocated to goodwill changed from $14,327,000 to $14,207,000. The value of all other assets acquired and liabilities assumed remained as previously reported. In addition, the change in purchase price had no impact on the Company’s current or previously reported results of operations. The combined entities have 25,000 metric tons of sulfonation capacity and a large, diverse customer portfolio. The acquisition expanded and diversified the Company’s customer base for sulfonated products in Brazil and provided an opportunity to sell the Company’s broader surfactant portfolio to over 1,200 new customers who benefit from the Company’s technical service and formulation support. The acquired businesses are included in the Company’s Surfactants segment. The acquisitions were accounted for as a business combination, and, accordingly, the assets acquired and liabilities assumed as part of the acquisition were measured and recorded at their estimated fair values. The following table summarizes the assets acquired and liabilities assumed: (Dollars in thousands) Assets: Current assets $ 5,165 Property, plant and equipment 5,716 Identifiable intangible assets 7,354 Goodwill 14,207 Total assets acquired $ 32,442 Liabilities: Current liabilities $ 408 Deferred tax liability 3,079 Total liabilities assumed $ 3,487 Net assets acquired $ 28,955 The acquired goodwill, which was assigned entirely to the Company’s Surfactant segment, is not tax deductible. The goodwill reflects the opportunity of introducing the Company’s broad line of surfactant products to the acquired entities’ large customer base. Identifiable intangible assets included customer relationships ($4,331,000), a supply contract ($2,555,000) and non-compete agreements ($468,000). The amortization period for these intangibles are 13 years, four years and five years, respectively. Tebras and PBC generated approximately $28,000,000 in net sales in 2015, with net income of less than $2,000,000. Pro forma financial information for 2015 and 2016 has not been included because revenues and earnings of the Company would not have been significantly different than reported had the acquisition date been January 1,2015. 2015 Acquisitions Business Acquisition On June 15, 2015, the Company acquired Procter & Gamble do Brasil S.A.’s (P&G Brazil’s) sulfonation production facility in Bahia, Brazil. The facility is located in northeastern Brazil and has 30,000 metric tons of surfactants capacity. The acquired business is included in the Company’s Surfactant segment. The acquired business complements the Company’s existing Vespasiano, Brazil, plant and provides opportunities to serve the growing northeastern Brazil market. The purchase price was $5,133,000. The acquisition was accounted for as a business combination and, accordingly, the assets acquired and liabilities assumed as part of the acquisition were measured and recorded at their estimated fair values. The purchase included property, plant and equipment valued at $6,007,000 and the assumption of liabilities valued at $874,000. No intangibles or goodwill were acquired in the business combination. The purchase price allocation is final, and no allocation adjustments were made to the amounts recorded at the acquisition date. Other acquisition-related expenses were not material. Post-acquisition financial results for the acquired business were insignificant. Pro forma financial information has not been included because revenues and earnings of the Company would not have been significantly different than reported had the acquisition date been January 1, 2014. See Note 22 for information regarding the subsequent impairment of assets at the Bahia, Brazil, site. Asset Acquisition In 2015, the Company purchased select chemical manufacturing assets and land from The Sun Products Corporation’s Pasadena, Texas, manufacturing site. The Company intends to redeploy the manufacturing assets as needed to reduce future capital expenditures. In addition, the Company is assessing options to produce nonionic surfactants and other products at the site. The purchase price of the land and manufacturing assets was $13,000,000, of which $3,377,000 was allocated to land and $9,623,000 was allocated to manufacturing assets.

Sale of Product Line

Sale of Product Line	12 Months Ended
	Dec. 31, 2017
Sale Of Product Line [Abstract]
Sale of Product Line	21. Sale of Product Line In January 2015, the Company sold its specialty polyurethane systems product line (kits) to J6 Polymers, LLC (J6) for cash of $3,262,000. Kits were part of the Company’s Polymers segment and accounted for approximately $2,800,000 of the Company’s 2014 net sales. The sale of kits included inventory, customer and supplier lists, formulations, manufacturing procedures and all other intellectual property associated with the manufacturing and selling of kits. As a result of the sale, Company operating income for the year ended December 31, 2015, included a gain of $2,862,000. The gain was attributed to the Polymer segment. J6 is a business wholly-owned and operated by members of the immediate family of Robert J. Wood, a former Company executive who retired from the Company in April 2014. Mr. Wood is a managing member of J6.

Business Restructuring and Asse

Business Restructuring and Asset Impairments	12 Months Ended
	Dec. 31, 2017
Restructuring And Related Activities [Abstract]
Business Restructuring and Asset Impairments	22. Business Restructuring and Asset Impairments 2017 Restructuring During the fourth quarter of 2017, the Company approved a plan to restructure a portion of its Fieldsboro, New Jersey production facility. This decision was made to improve future asset utilization and reduce the North American cost base going forward. The Company recorded $915,000 of restructuring expenses which reflected termination benefits for the plant employees. In addition, the Company reduced the useful lives of the manufacturing assets that were impacted by the restructuring and recorded $1,290,000 of accelerated depreciation. This expense was recorded in the cost of sales line of the consolidated statements of income. Also, in June 2017, the Company eliminated 11 positions from manufacturing operations at its Singapore plant. The Singapore plant is part of the Company’s Surfactant segment. The reduction in positions was made to better align the number of personnel with current business requirements and to reduce costs at that site. As a result of the reduction in workforce, termination expense of $132,000 was recognized in the second quarter of 2017 and there was no remaining liability for the termination pay as of December 31, 2017. 2016 Restructuring In May 2016, the Company announced plans to shut down its Longford Mills, Ontario, Canada (Longford Mills) manufacturing facility, a part of the Surfactant reportable segment, by December 31, 2016. The shutdown plan was developed as an effort to improve the Company’s asset utilization in North America and to reduce the Company’s fixed cost base. Manufacturing operation of the Longford Mills plant ceased by the end of 2016 and production of goods manufactured at the facility was moved to other Company North American production sites. In addition to the restructuring costs, the Company reduced the useful lives of the manufacturing assets in the Longford Mills plant. As a result, the Company recognized $4,471,000 of additional depreciation expense for the year ended December 31, 2016. The expense was included in the cost of sales line of the consolidated statements of income. No additional depreciation related to the change in the useful lives of the assets was recognized in 2017. Decommissioning of the assets continued throughout 2017 and $2,022,000 of decommissioning expense was recognized in 2017. As of December 31, 2017, an aggregate of $4,839,000 of expense has been recognized since the beginning of the restructuring, reflecting $1,594,000 of termination benefits for approximately 30 employees and $3,245,000 for other expenses principally related to site decommissioning costs. Site decommissioning costs will continue to be incurred in 2018. Below is a reconciliation of the beginning and ending balances of the Longford Mills restructuring liability: (In thousands) Termination Benefits Other Expense Total Restructuring liability at January 1, 2016 $ — $ — $ — Expense recognized 1,594 1,223 2,817 Amounts paid — (781 ) (781 ) Foreign currency translation (46 ) (5 ) (51 ) Restructuring liability at December 31, 2016 $ 1,548 $ 437 $ 1,985 Expense recognized - 2,022 2,022 Amounts paid (1,012 ) (2,377 ) (3,389 ) Foreign currency translation 56 17 73 Restructuring liability at December 31, 2017 $ 592 $ 99 $ 691 2016 Asset Impairments In the fourth quarter of 2016, the Company recorded pretax charges for asset impairments of $4,247,000, all related to the Company’s Surfactant segment (although the charges were excluded from the Surfactant segment operating results). In the United States, $2,297,000 of engineering and design costs associated with a planned nonionic surfactants plant construction project in Louisiana were written off from the Company’s construction-in-process account, as management decided to make nonionic surfactants at or near the Pasadena, Texas site the Company acquired from the Sun Products Corporation in 2015. In Brazil, the major customer for the Bahia plant exited the product line for which that plant supplied them product. As a result, the Company was required to recognize $1,950,000 of asset impairment expenses for the facility. Because the customer was under contract with the Company, a negotiated agreement was reached in 2016 whereby the customer agreed to compensate the Company in the lump-sum amount of $4,250,000 for lost future revenues. The compensation was reported in net sales for the year ended December 31, 2016.

Customer Claim Losses

Customer Claim Losses	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Customer Claims	23. Customer Claims In the fourth quarter of 2016, the Company established a reserve for two customer claims which alleged that product manufactured by the Company may have caused performance problems with the customers’ products. The combined amount of the reserve was $7,367,000, which was recorded as a reduction of net sales in the year ended December 31, 2016. Both claims related to the Company’s Surfactant segment. In the fourth quarter of 2017, the Company paid $2,709,000 for one of the claims and reversed the remainder of the reserve for the claim realizing $4,660,000 of income in 2017. The claim reversal was recorded within net sales. The second claim remains open.

Statement of Cash Flows - Nonca

Statement of Cash Flows - Noncash Investing and Financing Activities	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Statement of Cash Flows - Noncash Investing and Financing Activities	24. Statement of Cash Flows – Noncash Investing and Financing Activities Noncash investing activities included liabilities (accounts payable) incurred for fixed asset acquisitions of approximately $12,600,000, $10,410,000, and $9,515,000

TIORCO, LLC Joint Venture

TIORCO, LLC Joint Venture	12 Months Ended
	Dec. 31, 2017
Equity Method Investments And Joint Ventures [Abstract]
TIORCO, LLC Joint Venture	25. TIORCO, LLC Joint Venture In October 2015, the Company and its partner, Nalco Company (a subsidiary of Ecolab Inc.), made the decision to dissolve their equally owned and operated TIORCO, LLC (TIORCO) enhanced oil recovery joint venture. As a result of the dissolution, TIORCO incurred fourth quarter 2015 exit costs, which included termination pay, lease termination costs and asset impairments. The Company’s share of the exit costs was $2,356,000, which was reported in the ‘Loss from equity in joint venture’ line of the consolidated statement of income for the year ended December 31, 2015. The Company made a final cash investment of $2,900,000 to TIORCO during the three-month period ended March 31, 2016, to fund the exit costs and other final cash requirements for dissolving the joint venture. The legal dissolution of TIORCO is complete.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	26. Subsequent Events On January 30, 2018, the Company entered into a Credit Agreement among the Company, the foreign subsidiary borrowers from time to time party thereto, the lenders party thereto, JP Morgan Chase Bank, N.A., as administrative agent, Bank of America, N.A., as syndication agent, and J.P. Morgan Chase Bank, N.A. and Merrill Lynch Pierce Fenner & Smith Incorporated, as joint lead arrangers and joint bookrunners (the Credit Agreement). The Credit Agreement provides for a $350,000,000 multi-currency revolving credit facility, which matures on January 30, 2023. Under this five-year committed facility, the Company may draw as needed to finance working capital needs, permitted acquisitions and capital expenditures and for general corporate purposes. This new facility replaces the Company’s $125,000,000 multi-currency revolving credit agreement dated as of July 10, 2014. The Company is a party to (i) a Note Purchase Agreement dated as of September 29, 2005 (as amended, the 2005 NPA), pursuant to which the Company has issued (a) $40,000,000 in aggregate principal amount of its 5.69 percent Series 2005-A Senior Notes due November 1, 2018, (b) $40,000,000 in aggregate principal amount of its 5.88 percent Series 2010-A Senior Notes due June 1, 2022, and (c) $65,000,000 in aggregate principal amount of its 4.86 percent Series 2011-A Senior Notes due November 1, 2023, (ii) a Note Purchase Agreement dated as of June 27, 2013 (the 2013 NPA), pursuant to which the Company has issued $100,000,000 in aggregate principal amount of its 3.86 percent Senior Notes due June 27, 2025, and (iii) a Note Purchase Agreement dated as of July 10, 2015 (the 2015 NPA), pursuant to which the Company has issued $100,000,000 in aggregate principal amount of its 3.95 percent Senior Notes due July 10, 2027. Each of the 2005 NPA, the 2013 NPA and the 2015 NPA were amended effective January 30, 2018 to make certain covenants consistent with those included in the Credit Agreement.

Selected Quarterly Financial Da

Selected Quarterly Financial Data	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data	Selected Quarterly Financial Data (In thousands, except per share data) Unaudited 2017 Quarter First Second Third Fourth Year Net Sales $ 468,269 $ 495,101 $ 487,814 $ 473,823 $ 1,925,007 Gross Profit 92,098 89,966 75,602 80,599 338,265 Operating Income 46,059 38,961 30,309 30,831 146,160 Interest, net (2,992 ) (2,863 ) (2,763 ) (2,826 ) (11,444 ) Income Before Income Taxes 44,330 37,063 29,312 28,532 139,237 Net Income 31,912 27,896 21,853 9,886 91,547 Net Income Attributable to Stepan Company 31,913 27,882 21,899 9,884 91,578 Per Diluted Share 1.37 1.19 0.94 0.42 3.92 2016 Quarter First Second Third Fourth Year Net Sales $ 445,897 $ 454,603 $ 445,030 $ 420,636 $ 1,766,166 Gross Profit 93,499 92,931 83,395 68,720 338,545 Operating Income 44,607 42,916 28,738 9,932 126,193 Interest, net (3,614 ) (3,417 ) (2,824 ) (3,350 ) (13,205 ) Income Before Income Taxes 40,468 39,196 27,143 7,009 113,816 Net Income 27,919 28,501 21,367 8,411 86,198 Net Income Attributable to Stepan Company 27,916 28,496 21,362 8,417 86,191 Per Diluted Share 1.22 1.24 0.92 0.36 3.73

Summary of Significant Accoun37

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations Stepan Company (the Company) operations consist predominantly of the production and sale of specialty and intermediate chemicals, which are sold to other manufacturers for use in a variety of end products. Principal markets for all products are manufacturers of cleaning and washing compounds (including detergents, shampoos, fabric softeners, toothpastes and household cleaners), paints, cosmetics, food, beverages, nutritional supplements, agricultural products, plastics, furniture, automotive equipment, insulation and refrigeration.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (GAAP) requires Company management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the Company and all wholly and majority-owned subsidiaries in which the Company exercises controlling influence. The equity method is used to account for investments in which the Company exercises significant but noncontrolling influence. Intercompany balances and transactions are eliminated in consolidation. The Company has an 80 percent ownership interest in the Nanjing Stepan Jinling Chemical Limited Liability Company (a joint venture) and exercises controlling influence over the entity. Therefore, Nanjing Stepan Jinling Chemical Limited Liability Company’s accounts are included in the Company’s consolidated financial statements. The partner’s interest in the joint venture’s net income is reported in the net income attributable to noncontrolling interests line of the consolidated statements of income. The partner’s interest in the net assets of the joint venture is reported in the noncontrolling interests line (a component of equity separate from Company equity) of the consolidated balance sheets. Prior to 2016, the Company and Nalco Company (a subsidiary of Ecolab Inc.) equally owned and controlled TIORCO, LLC, a joint venture operated out of Denver, Colorado. In October 2015, the Company and Nalco Company made the decision to dissolve TIORCO, LLC. See Note 25 for information regarding the dissolution of the joint venture. Prior to the dissolution of the joint venture, the Company’s investment in TIORCO, LLC was accounted for using the equity method and was included in the other non-current assets line on the consolidated balance sheets. The Company’s share of joint venture’s net earnings was included in the loss from equity in joint ventures line of the consolidated statements of income.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with purchased maturities of three months or less to be cash equivalents. At December 31, 2017, the Company’s cash and cash equivalents totaled $298.9 million including $15.1 million in a money market fund, each of which was rated AAAm by Standard and Poor’s. Cash in U.S. demand deposit accounts totaled $131.9 million and cash of the Company’s non-U.S. subsidiaries held outside the U.S. totaled $151.9 million as of December 31, 2017.
Receivables and Credit Risk	Receivables and Credit Risk Receivables are stated net of allowances for doubtful accounts and other allowances and primarily include trade receivables from customers, as well as nontrade receivables from suppliers, governmental tax agencies and others. The Company is exposed to credit risk on accounts receivable balances. This risk is mitigated by the Company’s large, diverse customer base, which is dispersed over various geographic regions and industrial sectors. No single customer comprised more than 10 percent of the Company’s consolidated net sales in 2017, 2016 or 2015. The Company maintains allowances for potential credit losses. Specific customer allowances are recorded when a review of customer creditworthiness and current economic conditions indicate that collection is doubtful. The Company also maintains other customer allowances that occur in the normal course of business. Such allowances are based on historical averages and trade receivable levels. The following is an analysis of the allowance for doubtful accounts and other accounts receivable allowances for the years ended December 31, 2017, 2016 and 2015: (In thousands) 2017 2016 2015 Balance at January 1 $ 9,755 $ 8,046 $ 10,011 Provision charged to income 45 1,917 1,106 Accounts written off, net of recoveries 316 (208 ) (3,071 ) Balance at December 31 $ 10,116 $ 9,755 $ 8,046
Inventories	Inventories Inventories are valued at cost, which is not in excess of market value, and include material, labor and plant overhead costs. The last-in, first-out (LIFO) method is used to determine the cost of the Company’s U.S. inventories. The first-in, first-out (FIFO) method is used for all other inventories. Inventories priced at LIFO as of December 31, 2017 and 2016, accounted for 69 and 66
Property, Plant and Equipment	Property, Plant and Equipment Depreciation of property, plant and equipment is provided on a straight-line basis over the estimated useful lives of the assets. Lives used for calculating depreciation are generally 30 years for buildings and 15 years for building improvements. For assets classified as machinery and equipment, lives generally used for calculating depreciation expense range from 10 to 15 years for manufacturing equipment, five to 10 years for furniture and fixtures, three to five years for vehicles and three to 10 years for computer equipment and software. Manufacturing of chemicals is capital intensive with a large majority of the assets included in machinery and equipment representing manufacturing equipment. Major renewals and betterments are capitalized in the property accounts, while maintenance and repairs ($51,926,000 Included in the computer equipment and software component of machinery and equipment are costs related to the acquisition and development of internal-use software. Capitalized costs for internal-use software include external direct costs of materials and services consumed in obtaining and developing the software. For development projects where major internal resources are committed, payroll and payroll-related costs incurred during the application development phase of the project are also capitalized. The capitalized costs are amortized over the useful lives of the software, which are generally three to 10 years. Costs incurred in the preliminary project phase are expensed. Interest charges on borrowings applicable to major construction projects are capitalized. Property, plant and equipment assets are tested for impairment when events indicate that impairment may have occurred. See Note 22 for 2016 asset impairments.
Fair Value Measurements	Fair Value Measurements GAAP defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Furthermore, GAAP establishes a framework, in the form of a three-level hierarchy, for measuring fair value that prioritizes the inputs to valuation techniques used to measure fair value. The following describes the hierarchy levels: Level 1 - quoted prices in active markets for identical assets and liabilities. Level 2 - inputs other than quoted prices included within Level 1 that are directly or indirectly observable for the asset or liability, such as quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets and liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data. Level 3 - unobservable inputs which reflect the entity’s own assumptions about the assumptions market participants use in pricing the assets and liabilities. The Company applies the fair value measurement provisions of GAAP to any of its financial assets and liabilities that are carried at fair value on the consolidated balance sheets (see Note 2), its outstanding debt for disclosure purposes (also Note 2) and its pension plan assets (see Note 13). The Company also applies the fair value measurement requirements to nonrecurring fair value measurements of nonfinancial assets and liabilities recorded in conjunction with business combinations and as part of impairment reviews for goodwill and other long-lived assets.
Revenue Recognition	Revenue Recognition Revenue is recognized upon shipment of goods to customers at the time title and risk of loss pass to the customer. In a majority of instances this occurs when goods are provided to a carrier for shipment. For arrangements where the Company consigns product to a customer location, revenue is recognized when the customer uses the inventory. The Company records shipping and handling billed to a customer in a sales transaction as revenue. Costs incurred for shipping and handling are reported in cost of sales. Volume and cash discounts due customers are estimated and recorded in the same period as the sales to which the discounts relate and reported as reductions of revenue in the consolidated statements of income.
Cost of Sales	Cost of Sales Cost of sales comprises raw material costs (including inbound freight expense to deliver the raw materials), manufacturing plant labor expenses and various manufacturing overhead expenses, such as utility, maintenance, operating supply, amortization and manufacturing asset depreciation expenses. Cost of sales also includes outbound shipping and handling expenses, inter-plant transfer costs, warehouse expenses and rail car rental expenses.
Operating Expenses	Operating Expenses Selling expense comprises salary and the related fringe benefit expenses for marketing and sales personnel and operating costs, such as outside agent commissions, automobile rental and travel-related expenses, which support the sales and marketing functions. Bad debt charges and any depreciation expenses related to marketing assets (e.g., computers) are also classified as selling expense. Administrative expense comprises salary and the related fringe benefit expenses and operating costs for the Company’s various administrative functions, which include information services, finance, legal, and human resources. Environmental remediation expenses are also classified as administrative expense. The Company’s research and development costs are expensed as incurred. These expenses are aimed at discovery and commercialization of new knowledge with the intent that such effort will be useful in developing a new product or in bringing about a significant improvement to an existing product or process. Total research and development expenses were $33,169,000, $34,856,000, and $30,315,000 Compensation expense or income related to the Company’s deferred compensation plans is presented in the deferred compensation expense line in the Consolidated Statements of Income.
Environmental Expenditures	Environmental Expenditures Environmental expenditures that relate to current operations are expensed in cost of sales. Expenditures that mitigate or prevent environmental contamination and that benefit future operations are capitalized as assets and depreciated on a straight-line basis over the estimated useful lives of the assets, which are typically 10 years. Estimated future expenditures that relate to an existing condition caused by past operations, and which do not contribute to current or future revenue generation, are recorded as liabilities, with the corresponding charge recorded in administrative expenses, when environmental assessments and/or remedial efforts are probable and the cost or range of possible costs can be reasonably estimated. When no amount within the range is a better estimate than any other amount, the minimum amount in the range is accrued. Some of the factors on which the Company bases its estimates include information provided by feasibility studies, potentially responsible party negotiations and the development of remedial action plans. Legal costs related to environmental matters are expensed as incurred (see Note 16 for environmental contingencies).
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets The Company’s intangible assets include patents, agreements not to compete, trademarks, customer lists and relationships, technological and manufacturing know-how, supply contracts and goodwill, all of which were acquired as part of business or product line acquisitions. Intangible assets other than goodwill are determined to have either finite or indefinite useful lives. The Company currently has no indefinite-life intangible assets other than goodwill. The values for intangible assets with finite lives are amortized over the useful lives of the assets. Currently, the useful lives for the Company’s finite-lived intangible assets are as follows: patents – 10-15 years; non-compete agreements – five years; trademarks – 11 years; customer relationships – 10-13 years; supply contracts – four years and know-how – eight years. In addition, finite-life intangible assets are tested for impairment when events or changes in circumstances indicate that the carrying value of an intangible asset may not be recoverable. Goodwill is not amortized but is tested for impairment at least annually or more frequently if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit to which goodwill relates below the reporting unit’s carrying value. See Note 4 for detailed information about goodwill and other intangible assets.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. Deferred tax assets are recognized to the extent that we believe these assets are more likely than not to be realized. In making such a determination, we consider all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If we determine that we would be able to realize our deferred tax assets in the future in excess of their net recorded amount, we would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. Uncertain tax positions are recorded in accordance with ASC 740 on the basis of a two-step process whereby (1) we determine whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, we recognize the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within the income tax expense line in the accompanying Consolidated Statement of Operations. Accrued interest and penalties are included within the related tax liability line in the Consolidated Balance Sheet. The SEC staff issued Staff Accounting Bulletin 118 (“SAB 118”), which provides guidance on accounting for the tax effects of the U.S. Tax Cuts and Jobs Act (“Tax Act”). SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Act for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Act is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the Tax Act. See Note 9 for detailed information about income taxes including SAB 118 disclosures.
Translation of Foreign Currencies	Translation of Foreign Currencies For the Company’s consolidated foreign subsidiaries whose functional currency is the local foreign currency, assets and liabilities are translated into U.S. dollars at exchange rates in effect at year end and revenues and expenses are translated at average exchange rates for the year. Any resulting translation adjustments are included in the consolidated balance sheets in the accumulated other comprehensive loss line of stockholders’ equity. Gains or losses on foreign currency transactions are reflected in the other, net caption of the consolidated statements of income. The Company has two foreign subsidiaries whose functional currencies are the U.S. dollar. For these subsidiaries, nonmonetary assets and liabilities are translated at historical rates, monetary assets and liabilities are translated at exchange rates in effect at year end, revenues and expenses are translated at average exchange rates for the year and translation gains and losses are included in the other, net caption of the consolidated statements of income.
Stock-Based Compensation	Stock-Based Compensation The Company grants stock options, stock awards (including performance-based stock awards) and stock appreciation rights (SARs) to certain employees under its incentive compensation plans. The Company calculates the fair values of stock options, stock awards and SARs on the date such instruments are granted. The fair values of the stock options and stock awards are then recognized as compensation expense over the vesting periods of the instruments. The Company’s SARs granted before 2015 settle in cash. The cash-settled SARs are accounted for as liabilities that must be re-measured at fair value at the end of each reporting period. Compensation expense for each reporting period is calculated as the period-to-period change (or portion of the change, depending on the proportion of the vesting period that has been completed at the reporting date) in the fair value of the cash-settled SARs. SARs granted subsequent to 2014 are settled in shares of Company common stock. Compensation expense for the stock-settled SARs is calculated in the same way as compensation expense for stock options. See Note 11 for detailed information about the Company’s stock-based compensation.
Earnings Per Share	Earnings Per Share Basic earnings per share amounts are computed as net income attributable to the Company divided by the weighted-average number of common shares outstanding. Diluted earnings per share amounts are based on the weighted-average number of common shares outstanding plus the weighted-average of net common shares (under the treasury stock method) that would be outstanding assuming the exercise of outstanding stock options and stock-settled SARs, the vesting of unvested stock awards that have no performance or market condition and the issuance of contingent performance stock awards. See Note 18 for detailed information about the Company’s earnings per share calculations.
Comprehensive Income and Accumulated Other Comprehensive Income	Comprehensive Income and Accumulated Other Comprehensive Income Comprehensive income includes net income and all other non-owner changes in equity that are not reported in net income. Comprehensive income is disclosed in the consolidated statements of comprehensive income. Accumulated other comprehensive income (AOCI) is reported as a component of stockholders’ equity in the Company’s consolidated balance sheets. See Note 19 for detailed information regarding changes in the Company’s AOCI and reclassifications out of AOCI to income.
Segment Reporting	Segment Reporting The Company reports financial and descriptive information about its reportable operating segments. Operating segments are components of the Company that have separate financial information that is regularly evaluated by the chief operating decision maker to assess segment performance and allocate resources. The Company discloses segment revenue, operating income, assets, capital expenditures and depreciation and amortization expenses. Enterprise-wide financial information about the geographic locations in which the Company earns revenues and holds assets is also disclosed (see Note 17).
Derivative Instruments	Derivative Instruments Derivative instruments are recognized in the consolidated balance sheets as either assets or liabilities measured at fair value. For derivative instruments that are not designated as hedging instruments, changes in the fair values of the derivative instruments are recognized currently in earnings. For derivative instruments designated as hedging instruments, depending on the nature of the hedge, changes in the fair values of the derivative instruments are either offset in earnings against changes in the fair values of the hedged items or recognized in AOCI until the hedged transaction is recognized in earnings. At the time a hedging relationship is designated, the Company establishes the method it will use for assessing the effectiveness of the hedge and the measurement approach for determining the ineffective aspect of the hedge. Company policy prohibits the use of derivative instruments for trading or speculative purposes. See Note 3 for further information regarding the Company’s use of derivatives. At December 31, 2017, the Company held open forward contracts for the purchase of 0.8
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-9, Revenue from Contracts with Customers (Topic 606) Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date In February 2016, the FASB issued ASU No. 2016-2, Leases (Topic 842) In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory In January 2017, the FASB issued ASU No. 2017-4, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment In March 2017, the FASB issued ASU No. 2017-7, Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities In January 2018, the FASB issued ASU No. 2018-01, Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842

Summary of Significant Accoun38

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Allowance for Doubtful Accounts and Other Accounts Receivable Allowance	The following is an analysis of the allowance for doubtful accounts and other accounts receivable allowances for the years ended December 31, 2017, 2016 and 2015: (In thousands) 2017 2016 2015 Balance at January 1 $ 9,755 $ 8,046 $ 10,011 Provision charged to income 45 1,917 1,106 Accounts written off, net of recoveries 316 (208 ) (3,071 ) Balance at December 31 $ 10,116 $ 9,755 $ 8,046

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Values and Related Carrying Values of Debt	At December 31, 2017 and 2016, the fair values and related carrying values of debt, including current maturities, were as follows (the fair value and carrying value amounts are presented without regard to unamortized debt issuance costs of $987,000, and $1,141,000 December 31 (In thousands) 2017 2016 Fair value $ 293,272 $ 316,364 Carrying value 291,786 318,154
Financial Assets and Liabilities Measured on a Recurring Basis at Fair Value	The following tables present financial assets and liabilities measured on a recurring basis at fair value as of December 31, 2017 and 2016, and the level within the fair value hierarchy in which the fair value measurement falls: (In thousands) December 2017 Level 1 Level 2 Level 3 Mutual fund assets $ 28,270 $ 28,270 $ — $ — Derivative assets: Foreign currency contracts 335 — 335 — Total assets at fair value $ 28,605 $ 28,270 $ 335 $ — Derivative liabilities: Foreign currency contracts $ 94 $ — $ 94 $ — (In thousands) December 2016 Level 1 Level 2 Level 3 Mutual fund assets $ 24,055 $ 24,055 $ — $ — Derivative assets: Foreign currency contracts 453 — 453 — Total assets at fair value $ 24,508 $ 24,055 $ 453 $ — Derivative liabilities: Foreign currency contracts $ 469 $ — $ 469 $ — Total liabilities at fair value $ 469 $ — $ 469 $ —

Goodwill and Other Intangible40

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Changes in Carrying Value of Goodwill	The changes in the carrying value of goodwill for the years ended December 31, 2017 and 2016, were as follows: Surfactants Segment Polymer Segment Specialty Products Segment Total (In thousands) 2017 2016 2017 2016 2017 2016 2017 2016 Balance as of January 1 Goodwill $ 22,958 $ 8,869 $ 5,334 $ 5,380 $ 483 $ 483 $ 28,775 $ 14,732 Accumulated impairment loss (3,467 ) (3,467 ) — — — — (3,467 ) (3,467 ) Goodwill, net 19,491 5,402 5,334 5,380 483 483 25,308 11,265 Goodwill acquired (a) — 14,327 — — — — — 14,327 Goodwill measurement period adjustment (a) (120 ) — — — — — (120 ) — Foreign currency translation (211 ) (238 ) 141 (46 ) — — (70 ) (284 ) Balance as of December 31 Goodwill 22,627 22,958 5,475 5,334 483 483 28,585 28,775 Accumulated impairment loss (3,467 ) (3,467 ) — — — — (3,467 ) (3,467 ) Goodwill, net $ 19,160 $ 19,491 $ 5,475 $ 5,334 $ 483 $ 483 $ 25,118 $ 25,308
Components of Other Intangible Assets and Changes in Gross Carrying Values	The following table presents the components of other intangible assets, all of which have finite lives, as of December 31, 2017 and 2016. The year-over-year changes in gross carrying values mainly resulted from the effects of foreign currency translation. Gross Carrying Value Accumulated Amortization December 31 December 31 (In thousands) 2017 2016 2017 2016 Other Intangible Assets: Patents $ 6,947 $ 6,947 $ 3,893 $ 3,294 Non-compete agreements 453 $ 461 113 $ 15 Trademarks 4,087 4,087 1,870 1,525 Customer lists 12,150 12,238 4,299 3,337 Supply contract 2,476 2,521 774 105 Know-how (a) 8,043 8,043 4,669 3,682 Total $ 34,156 $ 34,297 $ 15,618 $ 11,958 (a) Know-how includes intellectual property rights covering proprietary information, written formulae, trade secrets or secret processes, inventions and developmental products (whether patentable or not), discoveries, improvements, compositions, manufacturing processes, manuals, specifications and technical data
Estimated Amortization Expense for Identifiable Intangibles Assets	Estimated amortization expense for identifiable intangibles assets for each of the five succeeding fiscal years is as follows: (In thousands) For year ended 12/31/18 $ 3,584 For year ended 12/31/19 3,584 For year ended 12/31/20 3,435 For year ended 12/31/21 2,025 For year ended 12/31/22 1,368

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Composition of Inventories	The composition of inventories was as follows: December 31 (In thousands) 2017 2016 Finished products $ 117,529 $ 127,597 Raw materials 55,219 46,066 Total inventories $ 172,748 $ 173,663

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt	Debt comprised the following at December 31, 2017 and 2016: (In thousands) Maturity Dates December 31, 2017 December 31, 2016 Unsecured private placement notes 3.95% (net of unamortized debt issuance cost of $346 and $382 for 2017 and 2016, respectively) 2021-2027 $ 99,654 $ 99,618 3.86% (net of unamortized debt issuance cost of $343 and $390 for 2017 and 2016, respectively) 2019-2025 99,657 99,610 4.86% (net of unamortized debt issuance cost of $191 and $225 for 2017 and 2016, respectively) 2018-2023 55,523 64,775 5.88% (net of unamortized debt issuance cost of $95 and $116 for 2017 and 2016, respectively) 2018-2022 28,476 34,170 5.69% (net of unamortized debt issuance cost of $12 and $28 for 2017 and 2016, respectively) 2018 5,703 11,400 Debt of foreign subsidiaries Unsecured bank debt, foreign currency 2018 1,786 432 Secured bank debt, foreign currency 2018 — 7,008 Total debt $ 290,799 $ 317,013 Less current maturities 22,500 28,154 Long-term debt $ 268,299 $ 288,859
Schedule of Net Interest Expense	Net interest expense for the years ended December 31, 2017, 2016 and 2015, comprised the following: (In thousands) 2017 2016 2015 Interest expense $ 14,428 $ 15,240 $ 15,488 Interest income (2,075 ) (1,247 ) (217 ) 12,353 13,993 15,271 Capitalized interest (909 ) (788 ) (738 ) Interest expense, net $ 11,444 $ 13,205 $ 14,533

Leased Properties (Tables)

Leased Properties (Tables)	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Consolidated Company Minimum Future Rental Payments Under Operating Leases With Initial or Remaining Noncancelable Lease Terms in Excess of One Year	Consolidated Company minimum future rental payments under operating leases with initial or remaining noncancelable lease terms in excess of one year as of December 31, 2017, are: (In thousands) Year 2018 $ 8,950 2019 6,659 2020 5,967 2021 4,683 2022 4,099 Subsequent to 2022 20,173 Total minimum future rental payments $ 50,531

Other, Net (Tables)

Other, Net (Tables)	12 Months Ended
	Dec. 31, 2017
Other Income And Expenses [Abstract]
Other Net in Consolidated Statements of Income	Other, net in the consolidated statements of income included the following for the years ended December 31, 2017, 2016 and 2015: (In thousands) 2017 2016 2015 Foreign exchange gains (losses) $ (646 ) $ (14 ) $ 686 Investment income 989 690 877 Realized and unrealized gains on investments 4,178 152 21 Other, net $ 4,521 $ 828 $ 1,584

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Provision for Taxes on Income and Other Related Income Before Taxes	The provisions for taxes on income and the related income before taxes for the years ended December 31, 2017, 2016 and 2015, were as follows: (In thousands) 2017 2016 2015 Taxes on Income Federal Current $ 32,299 $ 18,811 $ 7,697 Deferred (1,744 ) (3,192 ) 3,890 State Current 1,764 2,273 1,559 Deferred 192 (1,171 ) (225 ) Foreign Current 13,077 14,960 14,562 Deferred 2,102 (4,063 ) (664 ) Total $ 47,690 $ 27,618 $ 26,819 Income before Taxes Domestic $ 72,662 $ 64,675 $ 48,721 Foreign 66,575 49,141 54,135 Total $ 139,237 $ 113,816 $ 102,856
Summary of Variations Between the Effective and Statutory U.S. Federal Income Tax Rates	The variations between the effective and statutory U.S. federal income tax rates are summarized as follows: (In thousands) 2017 Amount % 2016 Amount % 2015 Amount % Federal income tax provision at statutory tax rate $ 48,733 35.0 $ 39,836 35.0 $ 36,000 35.0 State tax provision on income less applicable federal tax benefit 1,271 0.9 716 0.6 867 0.8 Foreign income taxed at different rates (8,075 ) (5.8 ) (6,325 ) (5.6 ) (5,060 ) (4.9 ) Repatriation of foreign earnings (1,054 ) (0.8 ) 14 — 21 — Unrecognized tax benefits (47 ) 0.0 23 — 1,536 1.5 Domestic production activities deduction (1,339 ) (1.0 ) (1,633 ) (1.4 ) (884 ) (0.9 ) Nontaxable foreign interest income (2,073 ) (1.5 ) (2,030 ) (1.8 ) (2,106 ) (2.0 ) U.S. tax reform, net impact (a) 14,807 10.7 — — — — Change in accounting method for depreciation (893 ) (0.6 ) — — — — Stock based compensation, excess tax benefits (b) (2,254 ) (1.6 ) (1,878 ) (1.7 ) — — U.S. tax credits (1,204 ) (0.9 ) (1,100 ) (1.0 ) (3,465 ) (3.4 ) Non-deductible expenses and other items, net (c) (182 ) (0.1 ) (5 ) 0.2 (90 ) — Total income tax provision $ 47,690 34.3 $ 27,618 24.3 $ 26,819 26.1 (a) Does not include state tax impacts, which are included in state tax provision on income less applicable federal tax benefit. (b) Excess tax benefits related to employee share-based payment transactions recognized in 2017 and 2016 resulting from the adoption of ASU No. 2016-9. There is no effect for 2015 because the recognition of excess tax benefits in the tax provision is to be done only on a prospective basis, beginning with the year of adopting the new guidance, which was 2016. (c) Certain 2016 and 2015 amounts have been reclassified to conform to the current year presentation.
Schedule Showing Tax Effects of Significant Temporary Differences Representing Deferred Tax Assets and Liabilities	At December 31, 2017 and 2016, the tax effects of significant temporary differences representing deferred tax assets and liabilities were as follows: (In thousands) 2017 2016 Deferred Tax Liabilities: Depreciation $ (51,244 ) $ (75,973 ) Unrealized foreign exchange loss (734 ) (631 ) Other (2,066 ) (2,756 ) $ (54,044 ) $ (79,360 ) Deferred Tax Assets: Pensions $ 7,884 $ 12,077 Deferred revenue 232 940 Other accruals and reserves 13,660 20,590 Inventories 1,182 1,815 Legal and environmental accruals 7,243 11,503 Deferred compensation 15,402 24,485 Bad debt and rebate reserves 2,865 4,195 Non-U.S. subsidiaries net operating loss carryforwards 2,657 1,201 Tax credit carryforwards 1,851 1,599 $ 52,976 $ 78,405 Valuation Allowance $ (2,255 ) $ (1,815 ) Net Deferred Tax Liabilities $ (3,323 ) $ (2,770 ) Reconciliation to Consolidated Balance Sheet: Non-current deferred tax assets (in other non-current assets) 7,639 9,727 Non-current deferred tax liabilities (10,962 ) (12,497 ) Net Deferred Tax (Liabilities) Assets $ (3,323 ) $ (2,770 )
Schedule of Reconciliations of Unrecognized Tax Benefits	Below are reconciliations of the January 1 and December 31 balances of unrecognized tax benefits for 2017, 2016 and 2015: (In thousands) 2017 2016 2015 Unrecognized tax benefits, opening balance $ 1,931 $ 1,958 $ 464 Gross increases – tax positions in prior period — — 1,526 Gross increases – current period tax positions 20 35 29 Foreign currency translation 69 (43 ) (37 ) Lapse of statute of limitations (93 ) (19 ) (24 ) Unrecognized tax benefits, ending balance $ 1,927 $ 1,931 $ 1,958

Stock-based Compensation (Table

Stock-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Fair Value Assumptions for Stock Options	The following are the weighted-average assumptions used to calculate the grant-date fair values of stock option awards granted in the years ended December 31, 2017, 2016 and 2015: For the Years Ended December 31 2017 2016 2015 Expected dividend yield 1.39% 1.45% 1.53% Expected volatility 30.01% 35.62% 40.32% Expected term 7.2 years 7.3 years 7.3 years Risk-free interest rate 2.22% 1.52% 1.96%
Summary of Stock Option Activity	A summary of stock option activity for the year ended December 31, 2017 is presented below: Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term Aggregate Intrinsic ($000) Options Outstanding at January 1, 2017 436,126 $ 42.99 Granted 71,434 78.56 Exercised (104,277 ) 32.32 Forfeited (11,478 ) 50.78 Outstanding at December 31, 2017 391,805 52.09 6.33 $ 10,532 Vested or expected to vest at December 31, 2017 384,777 51.95 6.29 10,396 Exercisable at December 31, 2017 230,118 47.62 4.77 7,214
Summary of Stock Award Activity	A summary of stock award activity for the year ended December 31, 2017, is presented below: Shares Weighted-Average Grant Fair Value Stock Awards Unvested at January 1, 2017 256,766 $ 40.74 Granted 40,171 75.94 Vested (113,738 ) 39.54 Forfeited (14,166 ) 45.93 Unvested at December 31, 2017 169,033
Summary of SARs Activity	The following is a summary of SARs activity for the year ended December 31, 2017: Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term Aggregate Intrinsic Value ($000) SARs Outstanding at January 1, 2017 553,582 $ 47.81 Granted 148,723 78.73 Exercised (73,739 ) 44.67 Forfeited (11,916 ) 68.95 Outstanding at December 31, 2017 616,650 55.23 7.46 $ 14,640

Postretirement Benefit Plans (T

Postretirement Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Obligations and Funded Status	Obligations and Funded Status at December 31 United States United Kingdom (In thousands) 2017 2016 2017 2016 Change in benefit obligation Benefit obligation at beginning of year $ 162,727 $ 160,789 $ 22,034 $ 19,950 Interest cost 6,651 6,934 592 733 Actuarial (gain) loss 9,109 1,538 (156 ) 5,614 Benefits paid (7,129 ) (6,534 ) (516 ) (513 ) Foreign exchange impact — — 2,094 (3,750 ) Benefit obligation at end of year $ 171,358 $ 162,727 $ 24,048 $ 22,034 United States United Kingdom (In thousands) 2017 2016 2017 2016 Change in plan assets Fair value of plan assets at beginning of year $ 137,092 $ 121,835 $ 20,336 $ 21,425 Actual return on plan assets 15,533 21,612 1,957 2,758 Employer contributions 2,412 179 365 378 Benefits paid (7,129 ) (6,534 ) (516 ) (513 ) Foreign exchange impact — — 2,026 (3,712 ) Fair value of plan assets at end of year $ 147,908 $ 137,092 $ 24,168 $ 20,336 Over (Under) funded status at end of year $ (23,450 ) $ (25,635 ) $ 120 $ (1,698 )
Schedule of Amounts Recognized in Balance Sheets	The amounts recognized in the consolidated balance sheets at December 31 consisted of United States United Kingdom (In thousands) 2017 2016 2017 2016 Non-current asset $ — $ — $ 120 — Current liability (302 ) (166 ) — — Non-current liability (23,148 ) (25,469 ) — (1,698 ) Net amount recognized $ (23,450 ) $ (25,635 ) $ 120 $ (1,698 )
Amounts Recognized in Accumulated Other Comprehensive Income	The amounts recognized in accumulated other comprehensive income at December 31 consisted of United States United Kingdom (In thousands) 2017 2016 2017 2016 Net actuarial loss $ 39,801 $ 40,022 $ 5,743 $ 7,443
Information for Pension Plans with Projected Benefit Obligations in Excess of Plan Assets	Below is information for pension plans with projected benefit obligations in excess of plan assets at December 31: United States United Kingdom (In thousands) 2017 2016 2017 2016 Projected benefit obligation $ 171,358 $ 162,727 $ — $ 22,034 Accumulated benefit obligation 171,358 162,727 — 22,034 Fair value of plan assets 147,908 137,092 — 20,336
Components of Net Periodic Benefit Cost	Net periodic benefit costs for the years ended December 31, 2017, 2016 and 2015, were as follows: United States United Kingdom (In thousands) 2017 2016 2015 2017 2016 2015 Interest cost $ 6,651 $ 6,934 $ 6,815 $ 592 $ 733 $ 789 Expected return on plan assets (9,288 ) (9,012 ) (9,579 ) (797 ) (900 ) (1,054 ) Amortization of net actuarial loss 3,085 3,386 4,534 382 77 179 Net periodic benefit cost $ 448 $ 1,308 $ 1,770 $ 177 $ (90 ) $ (86 )
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income	Other changes in plan assets and benefit obligations recognized in other comprehensive income for the years ended December 31, 2017, 2016 and 2015, were as follows: United States United Kingdom (In thousands) 2017 2016 2015 2017 2016 2015 Net actuarial (gain) loss $ 2,864 $ (11,062 ) $ (1,110 ) $ (1,318 ) $ 3,756 $ (781 ) Amortization of net actuarial loss (3,085 ) (3,386 ) (4,534 ) (382 ) (77 ) (179 ) Total recognized in other comprehensive income $ (221 ) $ (14,448 ) $ (5,644 ) $ (1,700 ) $ 3,679 $ (960 ) Total recognized in net periodic benefit cost and other comprehensive income $ 227 $ (13,140 ) $ (3,874 ) $ (1,523 ) $ 3,589 $ (1,046 )
Estimated Amounts Reclassified from Accumulated Other Comprehensive Income into Net Periodic Benefit Cost	The estimated amounts that will be reclassified from accumulated other comprehensive income into net periodic benefit cost in 2018 are as follows: (In thousands) United States United Kingdom Net actuarial loss $ 3,746 $ 222
Estimated Future Benefit Payments	Estimated Future Benefit Payments (In thousands) United States United Kingdom 2018 $ 7,560 $ 504 2019 7,956 511 2020 8,438 516 2021 8,973 539 2022 9,448 585 2023-2027 51,168 3,548
Defined Contribution Plan Expenses for Company's Retirement Savings Plans and Profit Sharing Plan	Defined contribution expenses for the Company’s qualified defined contribution plans were as follows: (In thousands) 2017 2016 2015 Retirement contributions $ 4,998 $ 4,902 $ 4,644 Profit sharing contributions 7,002 6,230 4,972 Total $ 12,000 $ 11,132 $ 9,616
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Company's Asset Allocations for its U.S. and U.K Pension Plans	The Company’s asset allocations for its U.S. pension plans at December 31, 2017 and 2016, by asset category, were as follows: December 31, 2017 (In thousands) Level 1 Level 2 Level 3 Total Cash and Cash Equivalents $ 4,903 $ — $ — $ 4,903 Equity Securities U.S. Equities 37,753 — — 37,753 Non-U.S. Equities 31,581 47 — 31,628 Employer Securities 30,197 — — 30,197 Total Equities 99,531 47 — 99,578 Fixed Income Securities U.S. Corporate Bonds — 28,744 — 28,744 U.S. Government and Agency Bonds 5,545 1,045 — 6,590 Other Bonds — 8,093 — 8,093 Total Fixed Income 5,545 37,882 — 43,427 Total $ 109,979 $ 37,929 $ — $ 147,908 December 31, 2016 (In thousands) Level 1 Level 2 Level 3 Total Cash and Cash Equivalents $ 3,633 $ 275 $ — $ 3,908 Equity Securities U.S. Equities 29,390 — — 29,390 Non-U.S. Equities 14,637 — — 14,637 Employer Securities 36,018 — — 36,018 Total Equities 80,045 — — 80,045 Fixed Income Securities U.S. Corporate Bonds — 28,278 — 28,278 U.S. Government and Agency Bonds 8,309 971 — 9,280 Other Bonds — 7,696 — 7,696 Total Fixed Income 8,309 36,945 — 45,254 Mutual Funds Real Estate 5,362 — — 5,362 Commodities 2,523 — — 2,523 Other — — — — Total Mutual Funds 7,885 — — 7,885 Total $ 99,872 $ 37,220 $ — $ 137,092
United Kingdom [Member]
Defined Benefit Plan Disclosure [Line Items]
Company's Asset Allocations for its U.S. and U.K Pension Plans	The Company’s asset allocations for its U.K. pension plans at December 31, 2017 and 2016, by asset category, were as follows: December 31, 2017 (In thousands) Level 1 Level 2 Level 3 Total Cash $ 745 $ — $ — $ 745 Equity Securities Pooled Pension Funds — 14,127 — 14,127 Fixed Income Pooled Pension Funds — 6,952 — 6,952 Real Estate Pooled Pension Funds — 646 — 646 Insurance Contracts — — 1,698 1,698 Total $ 745 $ 21,725 $ 1,698 $ 24,168 December 31, 2016 (In thousands) Level 1 Level 2 Level 3 Total Cash $ 243 $ — $ — $ 243 Equity Securities Pooled Pension Funds — 11,760 — 11,760 Fixed Income Pooled Pension Funds — 6,015 — 6,015 Real Estate Pooled Pension Funds — 559 — 559 Insurance Contracts — — 1,759 1,759 Total $ 243 $ 18,334 $ 1,759 $ 20,336
Fair Value Changes within Asset Categories for which Fair Value Measurements Use Significant Unobservable Inputs (Level 3) Defined Benefit United States Plans and United Kingdom Plans	Fair value changes within asset categories for which fair value measurements use significant unobservable inputs (Level 3) were as follows during 2016 and 2017: (In thousands) Insurance Fair value, December 31, 2015 $ 1,969 Sale proceeds (benefit payments) (144 ) Change in unrealized gain 265 Foreign exchange impact (331 ) Fair value, December 31, 2016 $ 1,759 Sale proceeds (benefit payments) (134 ) Change in unrealized gain (84 ) Foreign exchange impact 157 Fair value, December 31, 2017 $ 1,698
Defined Benefit Plan Periodic Costs [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-Average Assumptions Used to Determine Benefit Obligations/Net Periodic Benefit Costs	The weighted-average assumptions used to determine net periodic benefit costs for years ended December 31 were as follows: United States United Kingdom 2017 2016 2015 2017 2016 2015 Discount rate 4.17 % 4.39 % 4.09 % 2.60 % 4.00 % 3.50 % Expected long-term return on plan assets 7.00 % 7.00 % 7.50 % 3.77 % 4.59 % 4.66 %
Benefit Obligation [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-Average Assumptions Used to Determine Benefit Obligations/Net Periodic Benefit Costs	The weighted-average assumptions used to determine benefit obligations at December 31 were as follows: United States United Kingdom 2017 2016 2017 2016 Discount rate 3.67 % 4.17 % 2.40 % 2.60 %

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Payables And Accruals [Abstract]
Composition of Accrued Liabilities	The composition of accrued liabilities was as follows: December 31 (In thousands) 2017 2016 Accrued payroll and benefits $ 58,877 $ 66,575 Accrued customer rebates 16,729 18,553 Other accrued liabilities 17,170 25,667 Total accrued liabilities $ 92,776 $ 110,795

Other Non-Current Liabilities (

Other Non-Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Other Liabilities Disclosure [Abstract]
Composition of Other Non-Current Liabilities	The composition of other non-current liabilities was as follows: December 31 (In thousands) 2017 2016 Deferred revenue $ 1,539 $ 1,863 Environmental and legal matters 21,888 22,703 Deferred compensation liability 51,890 53,133 Pension liability 25,632 29,494 Other non-current liabilities 29,484 12,160 Total other non-current liabilities $ 130,433 $ 119,353

Segment Reporting (Tables)

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Operating Segment	The following is segment data for the three years ended December 31, 2017, 2016 and 2015: (In thousands) Surfactants Polymers Specialty Products Segment Totals 2017 Net sales $ 1,297,555 $ 546,634 $ 80,818 $ 1,925,007 Operating income 119,990 82,801 9,952 212,743 Assets 881,415 355,065 75,452 1,311,932 Capital expenditures 50,400 21,146 4,234 75,780 Depreciation and amortization expenses 49,102 22,998 5,019 77,119 2016 Net sales $ 1,181,563 $ 498,826 $ 85,777 $ 1,766,166 Operating income 99,796 96,788 10,698 207,282 Assets 831,324 301,890 75,483 1,208,697 Capital expenditures 64,121 31,890 4,194 100,205 Depreciation and amortization expenses 48,643 20,275 4,204 73,122 2015 Net sales $ 1,205,849 $ 491,488 $ 78,830 $ 1,776,167 Operating income 104,080 80,942 4,397 189,419 Assets 758,524 293,790 72,604 1,124,918 Capital expenditures 79,171 31,309 6,387 116,867 Depreciation and amortization expenses 42,122 19,541 3,659 65,322
Reconciliation of Segment Information to Consolidated Financial Statements	Below are reconciliations of segment data to the consolidated financial statements: (In thousands) 2017 2016 2015 Operating income - segment totals $ 212,743 $ 207,282 $ 189,419 Business restructuring and asset impairments (a) (3,069 ) (7,064 ) — Unallocated corporate expenses (b) (63,514 ) (74,025 ) (66,629 ) Total operating income 146,160 126,193 122,790 Interest expense, net (11,444 ) (13,205 ) (14,533 ) Loss from equity in joint ventures — — (6,985 ) Other, net 4,521 828 1,584 Consolidated income before income taxes $ 139,237 $ 113,816 $ 102,856 Assets - segment totals $ 1,311,932 $ 1,208,697 $ 1,124,918 Unallocated corporate assets (c) 158,929 145,193 113,474 Consolidated assets $ 1,470,861 $ 1,353,890 $ 1,238,392 Capital expenditures - segment totals $ 75,780 $ 100,205 $ 116,867 Unallocated corporate expenditures 2,833 2,871 2,482 Consolidated capital expenditures $ 78,613 $ 103,076 $ 119,349 Depreciation and amortization expenses – segment totals $ 77,119 $ 73,122 $ 65,322 Unallocated corporate depreciation expenses 1,903 1,845 1,663 Consolidated depreciation and amortization expenses $ 79,022 $ 74,967 $ 66,985 (a) See Note 22 regarding business restructuring and asset impairment costs. (b) Unallocated corporate expenses primarily comprise corporate administrative expenses (e.g., corporate finance, legal, human resources, information systems, deferred compensation and environmental remediation) that are not included in segment operating income and not used to evaluate segment performance. (c) The changes in unallocated corporate assets between 2017, 2016 and 2015 were primarily attributable to changes in the balance of U.S. cash and cash equivalents, which are not allocated to segments.
Summary of company-wide geographic data	Below is certain Company-wide geographic data for the years ended December 31, 2017, 2016 and 2015: (In thousands) 2017 2016 2015 Net sales (a) United States $ 1,159,578 $ 1,076,259 $ 1,069,526 France 176,052 151,031 169,072 Poland 188,244 153,986 150,654 United Kingdom 99,069 86,458 89,757 Brazil 109,960 74,961 63,439 All other countries 192,104 223,471 233,719 Total $ 1,925,007 $ 1,766,166 $ 1,776,167 Long-lived assets (b) United States $ 420,342 $ 411,023 $ 387,744 Germany 29,116 27,475 30,268 Singapore 33,530 36,270 39,181 Brazil (c) 55,974 58,106 26,721 China 30,849 29,508 25,689 United Kingdom 21,657 20,309 22,943 All other countries 50,631 47,670 52,139 Total $ 642,099 $ 630,361 $ 584,685 (a) Net sales are attributed to countries based on the location of the Company facility making the sales. (b) Includes net property, plant and equipment, goodwill and other intangible assets. (c) The change between 2016 and 2015 was attributable to the acquisition described in Note 20.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings Per Share	Below is the computation of basic and diluted earnings per share for the years ended December 31, 2017, 2016 and 2015. (In thousands, except per share amounts) 2017 2016 2015 Computation of Basic Earnings per Share Net income attributable to Stepan Company $ 91,578 $ 86,191 $ 75,968 Weighted-average number of shares outstanding 22,946 22,793 22,730 Basic earnings per share $ 3.99 $ 3.78 $ 3.34 Computation of Diluted Earnings per Share Net income attributable to Stepan Company $ 91,578 $ 86,191 $ 75,968 Weighted-average number of shares outstanding 22,946 22,793 22,730 Add weighted-average net shares from assumed exercise of options (under treasury share method) (a) 161 159 118 Add weighted-average net shares related to unvested stock awards (under treasury share method) 8 6 3 Add weighted-average net shares from assumed exercise of SARs (under treasury share method) 142 68 1 Add weighted-average contingently issuable net shares related to performance stock awards (under treasury share method) 120 68 6 Weighted-average shares applicable to diluted earnings 23,377 23,094 22,858 Diluted earnings per share $ 3.92 $ 3.73 $ 3.32 (a ) Options to purchase 18,630, 43,715 and 124,531 shares of common stock were not included in the computations of diluted earnings per share for the years ended December 31, 2017, 2016 and 2015, respectively. The options’ exercise prices were greater than the average market price for the common stock and the effect of the options on earnings per share would have been antidilutive.

Accumulated Other Comprehensi52

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Summary of Changes in Accumulated Other Comprehensive Income (Loss)	Below is the change in the Company’s accumulated other comprehensive income (loss) (AOCI) balance by component (net of income taxes) for the years ended December 31, 2017, 2016 and 2015: (In thousands) Foreign Currency Translation Adjustments Defined Benefit Pension Plan Adjustments Cash Flow Hedge Adjustments Total Balance at December 31, 2014 $ (42,914 ) $ (41,149 ) $ 118 $ (83,945 ) Other comprehensive income before reclassifications (45,423 ) 1,311 (49 ) (44,161 ) Amounts reclassified from AOCI — 3,013 5 3,018 Net current period other comprehensive income (45,423 ) 4,324 (44 ) (41,143 ) Balance at December 31, 2015 $ (88,337 ) $ (36,825 ) $ 74 $ (125,088 ) Other comprehensive income before reclassifications (8,438 ) 3,818 (19 ) (4,639 ) Amounts reclassified from AOCI — 2,217 45 2,262 Net current period other comprehensive income (8,438 ) 6,035 26 (2,377 ) Balance at December 31, 2016 $ (96,775 ) $ (30,790 ) $ 100 $ (127,465 ) Other comprehensive income before reclassifications 26,214 (582 ) — 25,632 Amounts reclassified from AOCI — 2,279 (9 ) 2,270 Net current period other comprehensive income 26,214 1,697 (9 ) 27,902 Balance at December 31, 2017 $ (70,561 ) $ (29,093 ) $ 91 $ (99,563 )
Summary of Amounts Reclassified Out of Accumulated Other Comprehensive Income	Amounts reclassified out of AOCI for the three years ended December 31, 2017, 2016 and 2015, is displayed below: Amounts Reclassified from AOCI (a) Affected Line Item in Consolidated (In thousands) 2017 2016 2015 Statements of Income Amortization of defined pension items: Prior service cost $ (14 ) $ (14 ) $ (17 ) Actuarial loss (3,509 ) (3,508 ) (4,757 ) $ (3,523 ) (3,522 ) (4,774 ) Total before tax (b) 1,244 1,305 1,761 Tax benefit $ (2,279 ) $ (2,217 ) $ (3,013 ) Net of tax Gains and losses on cash flow hedges: Interest rate contracts $ — $ (82 ) $ (22 ) Interest, net Foreign exchange contracts 9 9 9 Cost of sales 9 (73 ) (13 ) Total before tax 28 8 Tax benefit $ 9 $ (45 ) $ (5 ) Net of tax Total reclassifications for the period $ (2,270 ) $ (2,262 ) $ (3,018 ) Net of tax (a) Amounts in parentheses denote expense to statement of income. (b) This component of accumulated other comprehensive income is included in the computation of net periodic benefit cost (see Note 13 for details regarding net periodic benefit costs for the Company’s U.S. and U.K. defined benefit plans).

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Summary of Assets Acquired and Liabilities Assumed	The following table summarizes the assets acquired and liabilities assumed: (Dollars in thousands) Assets: Current assets $ 5,165 Property, plant and equipment 5,716 Identifiable intangible assets 7,354 Goodwill 14,207 Total assets acquired $ 32,442 Liabilities: Current liabilities $ 408 Deferred tax liability 3,079 Total liabilities assumed $ 3,487 Net assets acquired $ 28,955

Business Restructuring (Tables)

Business Restructuring (Tables)	12 Months Ended
	Dec. 31, 2017
2016 Restructuring [Member] | Longford Mills [Member]
Restructuring Cost And Reserve [Line Items]
Reconciliation of Restructuring Liability	Below is a reconciliation of the beginning and ending balances of the Longford Mills restructuring liability: (In thousands) Termination Benefits Other Expense Total Restructuring liability at January 1, 2016 $ — $ — $ — Expense recognized 1,594 1,223 2,817 Amounts paid — (781 ) (781 ) Foreign currency translation (46 ) (5 ) (51 ) Restructuring liability at December 31, 2016 $ 1,548 $ 437 $ 1,985 Expense recognized - 2,022 2,022 Amounts paid (1,012 ) (2,377 ) (3,389 ) Foreign currency translation 56 17 73 Restructuring liability at December 31, 2017 $ 592 $ 99 $ 691

Selected Quarterly Financial 55

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data	2017 Quarter First Second Third Fourth Year Net Sales $ 468,269 $ 495,101 $ 487,814 $ 473,823 $ 1,925,007 Gross Profit 92,098 89,966 75,602 80,599 338,265 Operating Income 46,059 38,961 30,309 30,831 146,160 Interest, net (2,992 ) (2,863 ) (2,763 ) (2,826 ) (11,444 ) Income Before Income Taxes 44,330 37,063 29,312 28,532 139,237 Net Income 31,912 27,896 21,853 9,886 91,547 Net Income Attributable to Stepan Company 31,913 27,882 21,899 9,884 91,578 Per Diluted Share 1.37 1.19 0.94 0.42 3.92 2016 Quarter First Second Third Fourth Year Net Sales $ 445,897 $ 454,603 $ 445,030 $ 420,636 $ 1,766,166 Gross Profit 93,499 92,931 83,395 68,720 338,545 Operating Income 44,607 42,916 28,738 9,932 126,193 Interest, net (3,614 ) (3,417 ) (2,824 ) (3,350 ) (13,205 ) Income Before Income Taxes 40,468 39,196 27,143 7,009 113,816 Net Income 27,919 28,501 21,367 8,411 86,198 Net Income Attributable to Stepan Company 27,916 28,496 21,362 8,417 86,191 Per Diluted Share 1.22 1.24 0.92 0.36 3.73

Summary of Significant Accoun56

Summary of Significant Accounting Policies - Additional Information (Detail) MMBTU in Millions	12 Months Ended
	Dec. 31, 2017USD ($)MMBTUCustomerSubsidiary	Dec. 31, 2016USD ($)Customer	Dec. 31, 2015USD ($)Customer	Dec. 31, 2014USD ($)
Summary Of Significant Accounting Policy [Line Items]
Cash and cash equivalents	$ 298,894,000	$ 225,743,000	$ 176,143,000	$ 85,215,000
Single customer comprised more than 10 percent of the Company's consolidated net sales | Customer	0	0	0
Percentage of LIFO Inventory	69.00%	66.00%
Cost of maintenance and repairs	$ 51,926,000	$ 51,530,000	$ 52,549,000
Total research and development expenses	$ 33,169,000	$ 34,856,000	$ 30,315,000
Capitalized Environmental expenditures depreciation period	10 years
Indefinite-life intangible assets	$ 0
Number of foreign subsidiaries | Subsidiary	2
Natural Gas [Member]
Summary Of Significant Accounting Policy [Line Items]
Volume in derivative contract | MMBTU	0.8
Purchased Contract Price	$ 2,521,000
Non-compete Agreements [Member]
Summary Of Significant Accounting Policy [Line Items]
Finite-lived intangible asset, useful life	5 years
Trademarks [Member]
Summary Of Significant Accounting Policy [Line Items]
Finite-lived intangible asset, useful life	11 years
Supply contracts [Member]
Summary Of Significant Accounting Policy [Line Items]
Finite-lived intangible asset, useful life	4 years
Know-how [Member]
Summary Of Significant Accounting Policy [Line Items]
Finite-lived intangible asset, useful life	8 years
Building [Member]
Summary Of Significant Accounting Policy [Line Items]
Lives used for calculating depreciation expense	30 years
Building Improvements [Member]
Summary Of Significant Accounting Policy [Line Items]
Lives used for calculating depreciation expense	15 years
Minimum [Member]
Summary Of Significant Accounting Policy [Line Items]
Percentage of Tax benefit recognized	50.00%
Minimum [Member] | Patents [Member]
Summary Of Significant Accounting Policy [Line Items]
Finite-lived intangible asset, useful life	10 years
Minimum [Member] | Customer Relationships [Member]
Summary Of Significant Accounting Policy [Line Items]
Finite-lived intangible asset, useful life	10 years
Minimum [Member] | Manufacturing Equipment [Member]
Summary Of Significant Accounting Policy [Line Items]
Lives used for calculating depreciation expense	10 years
Minimum [Member] | Furniture and Fixtures [Member]
Summary Of Significant Accounting Policy [Line Items]
Lives used for calculating depreciation expense	5 years
Minimum [Member] | Vehicles [Member]
Summary Of Significant Accounting Policy [Line Items]
Lives used for calculating depreciation expense	3 years
Minimum [Member] | Computers Equipment And Software [Member]
Summary Of Significant Accounting Policy [Line Items]
Lives used for calculating depreciation expense	3 years
Maximum [Member] | Patents [Member]
Summary Of Significant Accounting Policy [Line Items]
Finite-lived intangible asset, useful life	15 years
Maximum [Member] | Customer Relationships [Member]
Summary Of Significant Accounting Policy [Line Items]
Finite-lived intangible asset, useful life	13 years
Maximum [Member] | Manufacturing Equipment [Member]
Summary Of Significant Accounting Policy [Line Items]
Lives used for calculating depreciation expense	15 years
Maximum [Member] | Furniture and Fixtures [Member]
Summary Of Significant Accounting Policy [Line Items]
Lives used for calculating depreciation expense	10 years
Maximum [Member] | Vehicles [Member]
Summary Of Significant Accounting Policy [Line Items]
Lives used for calculating depreciation expense	5 years
Maximum [Member] | Computers Equipment And Software [Member]
Summary Of Significant Accounting Policy [Line Items]
Lives used for calculating depreciation expense	10 years
Money Market Funds [Member]
Summary Of Significant Accounting Policy [Line Items]
Cash and cash equivalents	$ 15,100,000
Demand Deposits [Member]
Summary Of Significant Accounting Policy [Line Items]
Cash and cash equivalents	131,900,000
Non-U.S. Subsidiaries [Member]
Summary Of Significant Accounting Policy [Line Items]
Cash and cash equivalents	$ 151,900,000
Nanjing Stepan Jinling Chemical Limited Liability Company [Member]
Summary Of Significant Accounting Policy [Line Items]
Ownership percentage	80.00%

Summary of Significant Accoun57

Summary of Significant Accounting Policies - Allowance for Doubtful Accounts and Other Accounts Receivable Allowances (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance For Doubtful Accounts Receivable Rollforward
Allowance, balance at the beginning	$ 9,755	$ 8,046	$ 10,011
Provision charged to income	45	1,917	1,106
Accounts written off, net of recoveries	316	(208)	(3,071)
Allowance, balance at ending	$ 10,116	$ 9,755	$ 8,046

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Unamortized debt issuance cost	$ 987,000	$ 1,141,000

Fair Value Measurements - Fair

Fair Value Measurements - Fair Values and Related Carrying Values of Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying value	$ 291,786	$ 318,154
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value	$ 293,272	$ 316,364

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Liabilities Measured on a Recurring Basis at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Mutual fund assets	$ 28,270	$ 24,055
Derivative assets:
Foreign currency contracts	335	453
Total assets at fair value	28,605	24,508
Derivative liabilities:
Foreign currency contracts	94	469
Total liabilities at fair value		469
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Mutual fund assets	28,270	24,055
Derivative assets:
Total assets at fair value	28,270	24,055
Level 2 [Member]
Derivative assets:
Foreign currency contracts	335	453
Total assets at fair value	335	453
Derivative liabilities:
Foreign currency contracts	$ 94	469
Total liabilities at fair value		$ 469

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative notional amount	$ 41,196,629	$ 33,372,000
Cash flow hedges [Member] | Interest rate contracts [Member]
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative notional amount	$ 0	$ 0	$ 3,724,000
Minimum [Member]
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative foreign currency exchange contracts durations	1 month
Maximum [Member]
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative foreign currency exchange contracts durations	3 months

Goodwill and Other Intangible62

Goodwill and Other Intangible Assets - Schedule of Changes in Carrying Value of Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 28,775	$ 14,732
Accumulated impairment loss, Beginning Balance	(3,467)	(3,467)
Goodwill net, Beginning Balance	25,308	11,265
Goodwill acquired		14,327
Goodwill measurement period adjustment	(120)
Foreign currency translation	(70)	(284)
Goodwill, Ending Balance	28,585	28,775
Accumulated impairment loss, Ending Balance	(3,467)	(3,467)
Goodwill net, Ending Balance	25,118	25,308
Surfactants Segment [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	22,958	8,869
Accumulated impairment loss, Beginning Balance	(3,467)	(3,467)
Goodwill net, Beginning Balance	19,491	5,402
Goodwill acquired		14,327
Goodwill measurement period adjustment	(120)
Foreign currency translation	(211)	(238)
Goodwill, Ending Balance	22,627	22,958
Accumulated impairment loss, Ending Balance	(3,467)	(3,467)
Goodwill net, Ending Balance	19,160	19,491
Polymer Segment [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	5,334	5,380
Goodwill net, Beginning Balance	5,334	5,380
Foreign currency translation	141	(46)
Goodwill, Ending Balance	5,475	5,334
Goodwill net, Ending Balance	5,475	5,334
Specialty Products Segment [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	483	483
Goodwill net, Beginning Balance	483	483
Goodwill, Ending Balance	483	483
Goodwill net, Ending Balance	$ 483	$ 483

Goodwill and Other Intangible63

Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Impairment of Goodwill	$ 0	$ 0
Amortization of Intangible Assets, Total	$ 3,711,000	$ 2,845,000	$ 2,816,000

Goodwill and Other Intangible64

Goodwill and Other Intangible Assets - Components of Other Intangible Assets and Changes in Gross Carrying Values (Detail) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Other Finite-Lived Intangible Assets, Gross Carrying Value		$ 34,156	$ 34,297
Other Finite-Lived Intangible Assets, Accumulated Amortization		15,618	11,958
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Other Finite-Lived Intangible Assets, Gross Carrying Value		6,947	6,947
Other Finite-Lived Intangible Assets, Accumulated Amortization		3,893	3,294
Non-compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Other Finite-Lived Intangible Assets, Gross Carrying Value		453	461
Other Finite-Lived Intangible Assets, Accumulated Amortization		113	15
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Other Finite-Lived Intangible Assets, Gross Carrying Value		4,087	4,087
Other Finite-Lived Intangible Assets, Accumulated Amortization		1,870	1,525
Customer Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Other Finite-Lived Intangible Assets, Gross Carrying Value		12,150	12,238
Other Finite-Lived Intangible Assets, Accumulated Amortization		4,299	3,337
Know-how [Member]
Finite-Lived Intangible Assets [Line Items]
Other Finite-Lived Intangible Assets, Gross Carrying Value	[1]	8,043	8,043
Other Finite-Lived Intangible Assets, Accumulated Amortization	[1]	4,669	3,682
Supply Contract [Member]
Finite-Lived Intangible Assets [Line Items]
Other Finite-Lived Intangible Assets, Gross Carrying Value		2,476	2,521
Other Finite-Lived Intangible Assets, Accumulated Amortization		$ 774	$ 105
[1]	Know-how includes intellectual property rights covering proprietary information, written formulae, trade secrets or secret processes, inventions and developmental products (whether patentable or not), discoveries, improvements, compositions, manufacturing processes, manuals, specifications and technical data

Goodwill and Other Intangible65

Goodwill and Other Intangible Assets - Estimated Amortization Expense for Identifiable Intangibles Assets (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]
For year ended 12/31/18	$ 3,584
For year ended 12/31/19	3,584
For year ended 12/31/20	3,435
For year ended 12/31/21	2,025
For year ended 12/31/22	$ 1,368

Inventories - Composition of In

Inventories - Composition of Inventories (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Finished products	$ 117,529	$ 127,597
Raw materials	55,219	46,066
Total inventories	$ 172,748	$ 173,663

Inventories - Additional Inform

Inventories - Additional Information (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
LIFO reserve	$ 33,518,000	$ 25,872,000

Debt - Debt (Detail)

Debt - Debt (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total debt	$ 290,799	$ 317,013
Less current maturities	22,500	28,154
Long-term debt	268,299	288,859
Unsecured private placement 3.95% note [Member]
Debt Instrument [Line Items]
Total debt	$ 99,654	$ 99,618
Debt instrument interest rate percentage	3.95%	3.95%
Unsecured private placement 3.95% note [Member] | Minimum [Member]
Debt Instrument [Line Items]
Maturity Dates	2,021	2,021
Unsecured private placement 3.95% note [Member] | Maximum [Member]
Debt Instrument [Line Items]
Maturity Dates	2,027	2,027
Unsecured private placement 3.86% note [Member]
Debt Instrument [Line Items]
Total debt	$ 99,657	$ 99,610
Debt instrument interest rate percentage	3.86%	3.86%
Unsecured private placement 3.86% note [Member] | Minimum [Member]
Debt Instrument [Line Items]
Maturity Dates	2,019	2,019
Unsecured private placement 3.86% note [Member] | Maximum [Member]
Debt Instrument [Line Items]
Maturity Dates	2,025	2,025
Unsecured private placement 4.86% note [Member]
Debt Instrument [Line Items]
Total debt	$ 55,523	$ 64,775
Debt instrument interest rate percentage	4.86%	4.86%
Unsecured private placement 4.86% note [Member] | Minimum [Member]
Debt Instrument [Line Items]
Maturity Dates	2,018	2,018
Unsecured private placement 4.86% note [Member] | Maximum [Member]
Debt Instrument [Line Items]
Maturity Dates	2,023	2,023
Unsecured private placement 5.88% note [Member]
Debt Instrument [Line Items]
Total debt	$ 28,476	$ 34,170
Debt instrument interest rate percentage	5.88%	5.88%
Unsecured private placement 5.88% note [Member] | Minimum [Member]
Debt Instrument [Line Items]
Maturity Dates	2,018	2,018
Unsecured private placement 5.88% note [Member] | Maximum [Member]
Debt Instrument [Line Items]
Maturity Dates	2,022	2,022
Unsecured private placement 5.69% note [Member]
Debt Instrument [Line Items]
Total debt	$ 5,703	$ 11,400
Debt instrument interest rate percentage	5.69%	5.69%
Maturity Dates	2,018	2,018
Debt of foreign subsidiaries Unsecured bank debt, foreign currency [Member]
Debt Instrument [Line Items]
Total debt	$ 1,786	$ 432
Maturity Dates	2,018	2,018
Debt of foreign subsidiaries Secured bank debt, foreign currency [Member]
Debt Instrument [Line Items]
Total debt		$ 7,008
Maturity Dates	2,018	2,018

Debt - Debt (Parenthetical) (De

Debt - Debt (Parenthetical) (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Unamortized debt issuance cost	$ 987,000	$ 1,141,000
Unsecured private placement 3.95% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	346,000	382,000
Unsecured private placement 3.86% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	343,000	390,000
Unsecured private placement 4.86% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	191,000	225,000
Unsecured private placement 5.88% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	95,000	116,000
Unsecured private placement 5.69% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	$ 12,000	$ 28,000

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	Jan. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total debt		$ 290,799,000	$ 317,013,000
Line of credit facility, Minimum maturity period		1 day
Line of credit facility, Maximum maturity period		180 days
Debt matures in 2018		$ 22,500,000
Debt matures in 2019		29,286,000
Debt matures in 2020		29,286,000
Debt matures in 2021		43,572,000
Debt matures in 2022		43,572,000
Debt matures after 2022		123,570,000
Amount of repayments of long-term debt due in next year		20,714,000
Amount of repayments of foreign subsidiaries short-term debt due in next year		$ 1,786,000
Minimum [Member]
Debt Instrument [Line Items]
Facility fee percentage		0.15%
Minimum [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Spread rate		0.975%
Minimum [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Spread rate		0.00%
Maximum [Member]
Debt Instrument [Line Items]
Facility fee percentage		0.35%
Maximum [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Spread rate		1.525%
Maximum [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Spread rate		0.525%
Unsecured Private Placement Notes [Member]
Debt Instrument [Line Items]
Total debt		$ 290,000,000
Unsecured Private Placement Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument interest rate percentage		3.86%
Maturity Dates		12 years
Unsecured Private Placement Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument interest rate percentage		5.88%
Maturity Dates		13 years
Multi currency revolving credit agreement [Member]
Debt Instrument [Line Items]
Revolving credit agreement		$ 125,000,000
Credit agreement secured date		Jul. 10, 2019
Debt Outstanding		$ 0
Letters of Credit Outstanding		4,677,000
Unused Revolving credit		120,323,000
Unrestricted retained earnings		190,495,000	$ 157,606,000
Multi currency revolving credit agreement [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Revolving credit agreement	$ 350,000,000
Credit agreement secured date	Jan. 30, 2023
Debt of foreign subsidiaries Unsecured bank debt and Term Loan, foreign currency [Member]
Debt Instrument [Line Items]
Total debt		$ 1,786,000

Debt - Schedule of Net Interest

Debt - Schedule of Net Interest Expense (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest Income Expense Net [Abstract]
Interest expense									$ 14,428	$ 15,240	$ 15,488
Interest income									(2,075)	(1,247)	(217)
Interest expense net of interest income									12,353	13,993	15,271
Capitalized interest									(909)	(788)	(738)
Interest expense, net	$ 2,826	$ 2,763	$ 2,863	$ 2,992	$ 3,350	$ 2,824	$ 3,417	$ 3,614	$ 11,444	$ 13,205	$ 14,533

Leased Properties - Additional

Leased Properties - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Leases [Abstract]
Total rental expense	$ 10,807,000	$ 8,595,000	$ 7,097,000

Leased Properties - Consolidate

Leased Properties - Consolidated Company Minimum Future Rental Payments Under Operating Leases with Initial or Remaining Noncancelable Lease Terms in Excess of One Year (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Leases [Abstract]
2,018	$ 8,950
2,019	6,659
2,020	5,967
2,021	4,683
2,022	4,099
Subsequent to 2022	20,173
Total minimum future rental payments	$ 50,531

Other, Net - Other Net in Conso

Other, Net - Other Net in Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Nonoperating Income Expense [Abstract]
Foreign exchange gains (losses)	$ (646)	$ (14)	$ 686
Investment income	989	690	877
Realized and unrealized gains on investments	4,178	152	21
Other, net	$ 4,521	$ 828	$ 1,584

Income Taxes - Schedule of Prov

Income Taxes - Schedule of Provision for Taxes on Income and Other Related Income Before Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Federal
Current									$ 32,299	$ 18,811	$ 7,697
Deferred									(1,744)	(3,192)	3,890
State
Current									1,764	2,273	1,559
Deferred									192	(1,171)	(225)
Foreign
Current									13,077	14,960	14,562
Deferred									2,102	(4,063)	(664)
Total									47,690	27,618	26,819
Income before Taxes
Domestic									72,662	64,675	48,721
Foreign									66,575	49,141	54,135
Income Before Provision for Income Taxes	$ 28,532	$ 29,312	$ 37,063	$ 44,330	$ 7,009	$ 27,143	$ 39,196	$ 40,468	$ 139,237	$ 113,816	$ 102,856

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax [Line Items]
Transition tax unrepatriated earnings foreign subsidiaries payable period		8 years
Net operating losses percentage		80.00%
Corporate tax rate		35.00%	35.00%	35.00%
Deferred tax assets		$ 31,800,000
Deferred tax liabilities		36,300,000
Deferred income tax benefit		4,500,000
Provisional transition tax obligation		19,400,000
Deferred tax liabilities noncurrent tax payable		18,100,000
Deferred tax liabilities current tax payable		1,300,000
Change in valuation allowance		0
Income tax expense		19,400,000
Tax loss carryforwards		10,352,000	$ 4,655,000
Tax credit carryforwards		1,851,000	1,599,000
Valuation Allowance		2,255,000	1,815,000
Unrecognized tax benefits		1,927,000	1,931,000	$ 1,958,000	$ 464,000
Unrecognized tax benefits that, if recognized, would impact effective tax rates		1,917,000	1,921,000	1,948,000
Recognition of interest and penalties accrued related to unrecognized tax benefits as income tax expense		3,000	9,000	$ 6,000
Income tax liability for interest and penalties		56,000	$ 53,000
Income tax return adjustments		0
Executive [Member]
Income Tax [Line Items]
Maximum deductible limitation for employee compensation		$ 1,000,000
Scenario Forecast [Member]
Income Tax [Line Items]
Corporate tax rate	21.00%
Maximum [Member]
Income Tax [Line Items]
Foreign tax credit percent		50.00%
Unrecognized tax benefits related to its current uncertain tax positions		$ 1,780,000

Income Taxes - Summary of Varia

Income Taxes - Summary of Variations Between the Effective and Statutory U.S. Federal Income Tax Rates (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal income tax provision at statutory tax rate		$ 48,733	$ 39,836	$ 36,000
State tax provision on income less applicable federal tax benefit		1,271	716	867
Foreign income taxed at different rates		(8,075)	(6,325)	(5,060)
Repatriation of foreign earnings		(1,054)	14	21
Unrecognized tax benefits		(47)	23	1,536
Domestic production activities deduction		(1,339)	(1,633)	(884)
Nontaxable foreign interest income		(2,073)	(2,030)	(2,106)
U.S. tax reform, net impact	[1]	14,807
Change in accounting method for depreciation		(893)
Stock based compensation, excess tax benefits	[2]	(2,254)	(1,878)
U.S. tax credits		(1,204)	(1,100)	(3,465)
Non-deductible expenses and other items, net	[3]	(182)	(5)	(90)
Total		$ 47,690	$ 27,618	$ 26,819
Percentage of Federal income tax provision at statutory tax rate		35.00%	35.00%	35.00%
Percentage of State tax provision on income less applicable federal tax benefit		0.90%	0.60%	0.80%
Percentage of Foreign income taxed at different rates		(5.80%)	(5.60%)	(4.90%)
Percentage of foreign earnings		(0.80%)
Percentage of Unrecognized tax benefits		0.00%		1.50%
Percentage of Domestic production activities deduction		(1.00%)	(1.40%)	(0.90%)
Percentage of Nontaxable foreign interest income		(1.50%)	(1.80%)	(2.00%)
Percentage of U.S. tax reform, net impact	[1]	10.70%
Percentage of Change in accounting method for depreciation		(0.60%)
Percentage of stock based compensation, excess tax benefits	[2]	(1.60%)	(1.70%)
Percentage of U.S. tax credits		(0.90%)	(1.00%)	(3.40%)
Percentage of Non-deductible expenses and other items, net	[3]	(0.10%)	0.20%
Percentage of Total income tax provision		34.30%	24.30%	26.10%
[1]	Does not include state tax impacts, which are included in state tax provision on income less applicable federal tax benefit.
[2]	Excess tax benefits related to employee share-based payment transactions recognized in 2017 and 2016 resulting from the adoption of ASU No. 2016-9. There is no effect for 2015 because the recognition of excess tax benefits in the tax provision is to be done only on a prospective basis, beginning with the year of adopting the new guidance, which was 2016.
[3]	Certain 2016 and 2015 amounts have been reclassified to conform to the current year presentation.

Income Taxes - Schedule Showing

Income Taxes - Schedule Showing Tax Effects of Significant Temporary Differences Representing Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Liabilities:
Depreciation	$ (51,244)	$ (75,973)
Unrealized foreign exchange loss	(734)	(631)
Other	(2,066)	(2,756)
Deferred Tax Liabilities, Gross	(54,044)	(79,360)
Deferred Tax Assets:
Pensions	7,884	12,077
Deferred revenue	232	940
Other accruals and reserves	13,660	20,590
Inventories	1,182	1,815
Legal and environmental accruals	7,243	11,503
Deferred compensation	15,402	24,485
Bad debt and rebate reserves	2,865	4,195
Non-U.S. subsidiaries net operating loss carryforwards	2,657	1,201
Tax credit carryforwards	1,851	1,599
Deferred Tax Assets, Gross	52,976	78,405
Valuation Allowance	(2,255)	(1,815)
Net Deferred Tax Liabilities	(3,323)	(2,770)
Reconciliation to Consolidated Balance Sheet:
Non-current deferred tax assets (in other non-current assets)	7,639	9,727
Non-current deferred tax liabilities	$ (10,962)	$ (12,497)

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliations of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, opening balance	$ 1,931	$ 1,958	$ 464
Gross increases – tax positions in prior period			1,526
Gross increases – current period tax positions	20	35	29
Foreign currency translation	69	(43)	(37)
Lapse of statute of limitations	(93)	(19)	(24)
Unrecognized tax benefits, ending balance	$ 1,927	$ 1,931	$ 1,958

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class Of Stock [Line Items]
Treasury stock, shares	3,561,509	3,470,084
Shares purchased during period	76,790	43,835	41,915
Treasury stock distributed under deferred compensation plan	7,965
Stock purchased to settle employees statutory withholding taxes relates to performance stock awards and deferred compensation distribution	22,598
Retirement Plans [Member]
Class Of Stock [Line Items]
Shares purchased during period	18,827
Open Market Repurchases [Member]
Class Of Stock [Line Items]
Shares purchased during period	57,963

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock authorized for share based payment awards under 2011 Plan	2,600,000
Shares available for grant under the 2011 plan	945,161
Compensation expenses	$ 7,151,000	$ 12,618,000	$ 4,374,000
Decrease increase in market value of company common stock, per share	$ 78.97	$ 81.48	$ 31.79
Income tax benefit recognized in the income statement for share-based compensation arrangements	$ 2,980,124	$ 4,761,000	$ 1,654,000
Proceeds from stock option exercises	$ 3,370,000	$ 4,017,000	777,000
Actual tax benefit recognized for the tax deductions from stock based compensation			$ 442,000
Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant-date fair values of options awarded	$ 24.49	$ 14.70	$ 15.59
Intrinsic values of options exercised	$ 5,232,000	$ 6,620,000	$ 1,426,000
Unrecognized compensation cost	$ 1,179,000
Weighted average period for amortization of unrecognized compensation cost	2 years
Actual tax benefit recognized for the tax deductions from stock based compensation	$ 1,455,000	$ 1,899,000	$ 351,000
Stock Option Granted Prior to 2017 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	2 years
Stock Options Granted in 2017 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
Vesting percentage for each year	33.33%
Performance Stock Award [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Performance stock awards vested	0
Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 3,737,000
Weighted average period for amortization of unrecognized compensation cost	1 year 6 months
Performance stock awards vested	113,738
Weighted-average grant-date fair values of awards granted	$ 75.94	$ 41.81	$ 39.11
SARs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period of expiration	10 years
Unrecognized compensation cost	$ 2,398,000
Weighted average period for amortization of unrecognized compensation cost	2 years
Weighted-average grant-date fair values of awards granted	$ 24.90	$ 14.69	$ 15.60
SARs liability cash-settled	$ 4,760,000	$ 5,832,000
SARs Granted Prior to 2017 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	2 years
SARs Granted in 2017 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
Vesting percentage for each year	33.33%
Maximum [Member] | Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period of expiration	10 years
Minimum [Member] | Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period of expiration	8 years

Stock-based Compensation - Fair

Stock-based Compensation - Fair Value Assumptions for Stock Options (Detail) - Stock Option [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield	1.39%	1.45%	1.53%
Expected volatility	30.01%	35.62%	40.32%
Expected term	7 years 2 months 12 days	7 years 3 months 18 days	7 years 3 months 18 days
Risk-free interest rate	2.22%	1.52%	1.96%

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Beginning Balance	436,126
Granted, Shares	71,434
Exercised, Shares	(104,277)	(167,675)	(45,289)
Forfeited, Shares	(11,478)
Shares, Ending Balance	391,805	436,126
Vested or expected to vest, Shares	384,777
Exercisable, Shares	230,118
Weighted Average Exercise Price, Beginning Balance	$ 42.99
Granted, Weighted Average Exercise Price	78.56
Exercised, Weighted Average Exercise Price	32.32
Forfeited, Weighted Average Exercise Price	50.78
Weighted Average Exercise Price, Ending Balance	52.09	$ 42.99
Vested or expected to vest, Weighted Average Exercise Price	51.95
Exercisable, Weighted Average Exercise Price	$ 47.62
Weighted Average Remaining Contractual Term, Ending Balance	6 years 3 months 29 days
Vested or expected to vest, Weighted Average Remaining Contractual Term	6 years 3 months 14 days
Exercisable, Weighted Average Remaining Contractual Term	4 years 9 months 7 days
Aggregate Intrinsic Value, Ending Balance	$ 10,532
Vested or expected to vest, Aggregate Intrinsic Value	10,396
Exercisable, Aggregate Intrinsic Value	$ 7,214

Stock-based Compensation - Su84

Stock-based Compensation - Summary of Stock Award Activity (Detail) - Stock Awards [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Beginning Balance	256,766
Granted, Shares	40,171
Vested, Shares	(113,738)
Forfeited, Shares	(14,166)
Shares, Ending Balance	169,033	256,766
Unvested Weighted Average Grant Date Fair Value, Beginning Balance	$ 40.74
Granted, Weighted Average Grant Date Fair Value	75.94	$ 41.81	$ 39.11
Vested, Weighted Average Grant Date Fair Value	39.54
Forfeited, Weighted Average Grant Date Fair Value	$ 45.93
Unvested Weighted Average Grant Date Fair Value, Ending Balance		$ 40.74

Stock-based Compensation - Su85

Stock-based Compensation - Summary of SARs Activity (Detail) - SARs [Member] $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Beginning Balance | shares	553,582
Granted, Shares | shares	148,723
Exercised, Shares | shares	(73,739)
Forfeited, Shares | shares	(11,916)
Shares, Ending Balance | shares	616,650
Weighted Average Exercise Price, Beginning Balance | $ / shares	$ 47.81
Granted, Weighted Average Exercise Price | $ / shares	78.73
Exercised, Weighted Average Exercise Price | $ / shares	44.67
Forfeited, Weighted Average Exercise Price | $ / shares	68.95
Weighted Average Exercise Price, Ending balance | $ / shares	$ 55.23
Weighted Average Remaining Contractual Term, Ending balance	7 years 5 months 15 days
Aggregate Intrinsic Value, Ending balance | $	$ 14,640

Deferred Compensation - Additio

Deferred Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Deferred compensation	$ 4,857,000	$ 16,805,000	$ 6,500,000
Deferred compensation liability	$ 58,915,000	$ 60,328,000

Postretirement Benefit Plans -

Postretirement Benefit Plans - Obligations and Funded Status (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
United States [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Benefit obligation at beginning of year	$ 162,727	$ 160,789
Interest cost	6,651	6,934	$ 6,815
Actuarial (gain) loss	9,109	1,538
Benefits paid	(7,129)	(6,534)
Benefit obligation at end of year	171,358	162,727	160,789
Fair value of plan assets at beginning of year	137,092	121,835
Actual return on plan assets	15,533	21,612
Employer contributions	2,412	179
Benefits paid	(7,129)	(6,534)
Fair value of plan assets at end of year	147,908	137,092	121,835
Over (Under) funded status at end of year	(23,450)	(25,635)
United Kingdom [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Benefit obligation at beginning of year	22,034	19,950
Interest cost	592	733	789
Actuarial (gain) loss	(156)	5,614
Benefits paid	(516)	(513)
Foreign exchange impact	2,094	(3,750)
Benefit obligation at end of year	24,048	22,034	19,950
Fair value of plan assets at beginning of year	20,336	21,425
Actual return on plan assets	1,957	2,758
Employer contributions	365	378
Benefits paid	(516)	(513)
Foreign exchange impact	2,026	(3,712)
Fair value of plan assets at end of year	24,168	20,336	$ 21,425
Over (Under) funded status at end of year	$ 120	$ (1,698)

Postretirement Benefit Plans 88

Postretirement Benefit Plans - Schedule of Amounts Recognized in Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
United States [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Current liability	$ (302)	$ (166)
Non-current liability	(23,148)	(25,469)
Net amount recognized	(23,450)	(25,635)
United Kingdom [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Non-current asset	120
Non-current liability		(1,698)
Net amount recognized	$ 120	$ (1,698)

Postretirement Benefit Plans 89

Postretirement Benefit Plans - Amounts Recognized in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
United States [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net actuarial loss	$ 39,801	$ 40,022
United Kingdom [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net actuarial loss	$ 5,743	$ 7,443

Postretirement Benefit Plans 90

Postretirement Benefit Plans - Information for Pension Plans with Projected Benefit Obligations in Excess of Plan Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
United States [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Projected benefit obligation	$ 171,358	$ 162,727
Accumulated benefit obligation	171,358	162,727
Fair value of plan assets	$ 147,908	137,092
United Kingdom [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Projected benefit obligation		22,034
Accumulated benefit obligation		22,034
Fair value of plan assets		$ 20,336

Postretirement Benefit Plans 91

Postretirement Benefit Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 6,651	$ 6,934	$ 6,815
Expected return on plan assets	(9,288)	(9,012)	(9,579)
Amortization of net actuarial loss	3,085	3,386	4,534
Net periodic benefit cost	448	1,308	1,770
United Kingdom [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	592	733	789
Expected return on plan assets	(797)	(900)	(1,054)
Amortization of net actuarial loss	382	77	179
Net periodic benefit cost	$ 177	$ (90)	$ (86)

Postretirement Benefit Plans 92

Postretirement Benefit Plans - Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
United States [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net actuarial (gain) loss	$ 2,864	$ (11,062)	$ (1,110)
Amortization of net actuarial loss	(3,085)	(3,386)	(4,534)
Total recognized in other comprehensive income	(221)	(14,448)	(5,644)
Total recognized in net periodic benefit cost and other comprehensive income	227	(13,140)	(3,874)
United Kingdom [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net actuarial (gain) loss	(1,318)	3,756	(781)
Amortization of net actuarial loss	(382)	(77)	(179)
Total recognized in other comprehensive income	(1,700)	3,679	(960)
Total recognized in net periodic benefit cost and other comprehensive income	$ (1,523)	$ 3,589	$ (1,046)

Postretirement Benefit Plans 93

Postretirement Benefit Plans - Estimated Amounts Reclassified from Accumulated Other Comprehensive Income into Net Periodic Benefit Cost (Detail) $ in Thousands	Dec. 31, 2017USD ($)
United States [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net actuarial loss	$ 3,746
United Kingdom [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net actuarial loss	$ 222

Postretirement Benefit Plans 94

Postretirement Benefit Plans - Estimated Future Benefit Payments (Detail) $ in Thousands	Dec. 31, 2017USD ($)
United States [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
2,018	$ 7,560
2,019	7,956
2,020	8,438
2,021	8,973
2,022	9,448
2023-2027	51,168
United Kingdom [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
2,018	504
2,019	511
2,020	516
2,021	539
2,022	585
2023-2027	$ 3,548

Postretirement Benefit Plans 95

Postretirement Benefit Plans - Weighted-Average Assumptions Used To Determine Benefit Obligations (Detail)	Dec. 31, 2017	Dec. 31, 2016
United States [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Discount rate	3.67%	4.17%
United Kingdom [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Discount rate	2.40%	2.60%

Postretirement Benefit Plans 96

Postretirement Benefit Plans - The Weighted Average Assumptions Used to Determine Net Periodic Benefit Costs (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
United States [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Discount rate	4.17%	4.39%	4.09%
Expected long-term return on plan assets	7.00%	7.00%	7.50%
United Kingdom [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Discount rate	2.60%	4.00%	3.50%
Expected long-term return on plan assets	3.77%	4.59%	4.66%

Postretirement Benefit Plans 97

Postretirement Benefit Plans - Defined Benefit Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 20, 2017	Feb. 21, 2017	Feb. 23, 2016
Defined Benefit Plan Disclosure [Line Items]
Assets gains or losses added for prior year	80.00%
Assets gains or losses added for second preceding year	60.00%
Assets gains or losses added for third preceding year	40.00%
Assets gains or losses added for fourth preceding year	20.00%
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Common shares sold to the Company's ESOP trust				18,827	40,837	56,894
Expected long-term rate of return on assets	7.00%	7.00%	7.50%
Expected payment related to qualified plan	$ 0
Expected payment related to non-qualified plan	$ 302,000
U.K Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on assets	3.77%	4.59%	4.66%
Percentage of premium estimated return for equities and properties to risk free rate	3.00%
Percentage of long term return in cash	4.00%
Expected payment related to qualified plan	$ 461,000
Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of target allocation for investment category	50.00%
Expected long-term rate of return on assets	6.31%
Equities [Member] | U.K Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of target allocation for investment category	58.00%
Debt Securities [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of target allocation for investment category	30.00%
Debt Securities [Member] | U.K Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of target allocation for investment category	29.00%
Employer Securities [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of target allocation for investment category	20.00%
Insurance Contracts [Member] | U.K Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of target allocation for investment category	7.00%
Real Estate Fund [Member] | U.K Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of target allocation for investment category	3.00%
Cash [Member] | U.K Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of target allocation for investment category	3.00%
U.S. and international equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on assets	4.69%

Postretirement Benefit Plans 98

Postretirement Benefit Plans - Company's Asset Allocations for its U.S. Pension Plans by Asset Category (Detail) - United States [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Total	$ 147,908	$ 137,092	$ 121,835
Commodities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		2,523
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	109,979	99,872
Level 1 [Member] | Commodities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		2,523
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	37,929	37,220
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,903	3,908
Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,903	3,633
Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		275
U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	37,753	29,390
U.S. Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	37,753	29,390
Non-U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	31,628	14,637
Non-U.S. Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	31,581	14,637
Non-U.S. Equities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	47
Employer Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	30,197	36,018
Employer Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	30,197	36,018
Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	99,578	80,045
Equities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	99,531	80,045
Equities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	47
U.S. Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	28,744	28,278
U.S. Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	28,744	28,278
U.S. Government and Agency Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	6,590	9,280
U.S. Government and Agency Bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	5,545	8,309
U.S. Government and Agency Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	1,045	971
Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	8,093	7,696
Other Bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	8,093	7,696
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	43,427	45,254
Debt Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	5,545	8,309
Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	$ 37,882	36,945
Real Estate Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		5,362
Real Estate Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		5,362
Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Total		7,885
Mutual Funds | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		$ 7,885

Postretirement Benefit Plans 99

Postretirement Benefit Plans - Company's Asset Allocations for its U.K. Pension Plans by Asset Category (Detail) - United Kingdom [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Total	$ 24,168	$ 20,336	$ 21,425
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	745	243
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	21,725	18,334
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	1,698	1,759
Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	745	243
Cash [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	745	243
Pooled Pension Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	14,127	11,760
Pooled Pension Funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	14,127	11,760
Pooled Fixed Pension Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	6,952	6,015
Pooled Fixed Pension Funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	6,952	6,015
Real Estate Pooled Pension Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	646	559
Real Estate Pooled Pension Funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	646	559
Insurance Contracts [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	1,698	1,759
Insurance Contracts [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	$ 1,698	$ 1,759

Postretirement Benefit Plans100

Postretirement Benefit Plans - Fair Value Changes Within Asset Categories for which Fair Value Measurements Use Significant Unobservable Inputs Level 3 (Detail) - Insurance Contracts [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 1,759	$ 1,969
Sale proceeds (benefit payments)	(134)	(144)
Change in unrealized gain	(84)	265
Foreign exchange impact	157	(331)
Ending balance	$ 1,698	$ 1,759

Postretirement Benefit Plans101

Postretirement Benefit Plans - Defined Contribution Plan Expenses for the Company's Retirement Savings Plans and Profit Sharing Plan (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
Total defined contribution expense	$ 12,000	$ 11,132	$ 9,616
Retirement Contributions [Member]
Defined Contribution Plan Disclosure [Line Items]
Total defined contribution expense	4,998	4,902	4,644
Profit Sharing Contributions [Member]
Defined Contribution Plan Disclosure [Line Items]
Total defined contribution expense	$ 7,002	$ 6,230	$ 4,972

Postretirement Benefit Plans102

Postretirement Benefit Plans - Defined Contribution Plans - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
Supplemental plan liability balances	$ 1,661	$ 1,767
Defined contribution plan expense	12,000	11,132	$ 9,616
Statutory Plans [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan expense	398	290	$ 1,375
Defined Contribution Plans [Member]
Defined Contribution Plan Disclosure [Line Items]
Balance of trust assets	$ 1,587	$ 1,692

Accrued Liabilities - Compositi

Accrued Liabilities - Composition of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Accrued payroll and benefits	$ 58,877	$ 66,575
Accrued customer rebates	16,729	18,553
Other accrued liabilities	17,170	25,667
Total accrued liabilities	$ 92,776	$ 110,795

Other Non-Current Liabilities -

Other Non-Current Liabilities - Statement of Composition of Other Non Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Liabilities Disclosure [Abstract]
Deferred revenue	$ 1,539	$ 1,863
Environmental and legal matters	21,888	22,703
Deferred compensation liability	51,890	53,133
Pension liability	25,632	29,494
Other non-current liabilities	29,484	12,160
Total other non-current liabilities	$ 130,433	$ 119,353

Contingencies - Additional Info

Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Site Contingency [Line Items]
Environmental and legal losses	$ 24,200,000	$ 25,800,000
Cash outlays related to legal and environmental matters	$ 2,000,000	$ 1,400,000
Contribution for future response costs	5.00%
Wilmington Site [Member]
Site Contingency [Line Items]
Payment of environmental response costs	$ 2,500,000
Minimum [Member]
Site Contingency [Line Items]
Environmental and legal losses	24,200,000
Maximum [Member]
Site Contingency [Line Items]
Environmental and legal losses	$ 45,400,000

Segment Reporting - Additional

Segment Reporting - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017Segment
Segment Reporting [Abstract]
Number of reportable segments	3

Segment Reporting - Operating S

Segment Reporting - Operating Segment (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Segment Reporting Information [Line Items]
Net sales	$ 473,823	$ 487,814	$ 495,101	$ 468,269	$ 420,636	$ 445,030	$ 454,603	$ 445,897	$ 1,925,007	[1]	$ 1,766,166	[1]	$ 1,776,167	[1]
Operating income	30,831	$ 30,309	$ 38,961	$ 46,059	9,932	$ 28,738	$ 42,916	$ 44,607	146,160		126,193		122,790
Assets	1,470,861				1,353,890				1,470,861		1,353,890		1,238,392
Capital expenditures									78,613		103,076		119,349
Depreciation and amortization expenses									79,022		74,967		66,985
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									1,925,007		1,766,166		1,776,167
Operating income									212,743		207,282		189,419
Assets	1,311,932				1,208,697				1,311,932		1,208,697		1,124,918
Capital expenditures									75,780		100,205		116,867
Depreciation and amortization expenses									77,119		73,122		65,322
Surfactants [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									1,297,555		1,181,563		1,205,849
Operating income									119,990		99,796		104,080
Assets	881,415				831,324				881,415		831,324		758,524
Capital expenditures									50,400		64,121		79,171
Depreciation and amortization expenses									49,102		48,643		42,122
Polymers [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									546,634		498,826		491,488
Operating income									82,801		96,788		80,942
Assets	355,065				301,890				355,065		301,890		293,790
Capital expenditures									21,146		31,890		31,309
Depreciation and amortization expenses									22,998		20,275		19,541
Specialty Products [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									80,818		85,777		78,830
Operating income									9,952		10,698		4,397
Assets	$ 75,452				$ 75,483				75,452		75,483		72,604
Capital expenditures									4,234		4,194		6,387
Depreciation and amortization expenses									$ 5,019		$ 4,204		$ 3,659
[1]	Net sales are attributed to countries based on the location of the Company facility making the sales.

Segment Reporting - Reconciliat

Segment Reporting - Reconciliation of Segment Information to Consolidated Financial Statements (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Operating income		$ 30,831	$ 30,309	$ 38,961	$ 46,059	$ 9,932	$ 28,738	$ 42,916	$ 44,607	$ 146,160	$ 126,193	$ 122,790
Business restructuring and asset impairments										(3,069)	(7,064)
Interest expense, net		(2,826)	(2,763)	(2,863)	(2,992)	(3,350)	(2,824)	(3,417)	(3,614)	(11,444)	(13,205)	(14,533)
Loss from equity in joint ventures												(6,985)
Other, net										4,521	828	1,584
Consolidated income before income taxes		28,532	$ 29,312	$ 37,063	$ 44,330	7,009	$ 27,143	$ 39,196	$ 40,468	139,237	113,816	102,856
Assets		1,470,861				1,353,890				1,470,861	1,353,890	1,238,392
Capital expenditures										78,613	103,076	119,349
Depreciation and amortization										79,022	74,967	66,985
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating income										212,743	207,282	189,419
Assets		1,311,932				1,208,697				1,311,932	1,208,697	1,124,918
Capital expenditures										75,780	100,205	116,867
Depreciation and amortization										77,119	73,122	65,322
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Business restructuring and asset impairments	[1]									(3,069)	(7,064)
Unallocated corporate expenses	[2]									(63,514)	(74,025)	(66,629)
Unallocated corporate assets		$ 158,929				$ 145,193				158,929	145,193	113,474
Unallocated corporate expenditures										2,833	2,871	2,482
Unallocated corporate depreciation expenses										$ 1,903	$ 1,845	$ 1,663
[1]	See Note 22 regarding business restructuring and asset impairment costs.
[2]	Unallocated corporate expenses primarily comprise corporate administrative expenses (e.g., corporate finance, legal, human resources, information systems, deferred compensation and environmental remediation) that are not included in segment operating income and not used to evaluate segment performance.

Segment Reporting - Summary of

Segment Reporting - Summary of Company Wide Geographic Data (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Schedule Of Geographical Segments [Line Items]
Net sales		$ 473,823	$ 487,814	$ 495,101	$ 468,269	$ 420,636	$ 445,030	$ 454,603	$ 445,897	$ 1,925,007	[1]	$ 1,766,166	[1]	$ 1,776,167	[1]
Long-lived assets	[2]	642,099				630,361				642,099		630,361		584,685
United States [Member]
Schedule Of Geographical Segments [Line Items]
Net sales	[1]									1,159,578		1,076,259		1,069,526
Long-lived assets	[2]	420,342				411,023				420,342		411,023		387,744
France [Member]
Schedule Of Geographical Segments [Line Items]
Net sales	[1]									176,052		151,031		169,072
Poland [Member]
Schedule Of Geographical Segments [Line Items]
Net sales	[1]									188,244		153,986		150,654
United Kingdom [Member]
Schedule Of Geographical Segments [Line Items]
Net sales	[1]									99,069		86,458		89,757
Long-lived assets	[2]	21,657				20,309				21,657		20,309		22,943
All Other Countries [Member]
Schedule Of Geographical Segments [Line Items]
Net sales	[1]									192,104		223,471		233,719
Long-lived assets	[2]	50,631				47,670				50,631		47,670		52,139
Brazil [Member]
Schedule Of Geographical Segments [Line Items]
Net sales	[1]									109,960		74,961		63,439
Long-lived assets	[2],[3]	55,974				58,106				55,974		58,106		26,721
Germany [Member]
Schedule Of Geographical Segments [Line Items]
Long-lived assets	[2]	29,116				27,475				29,116		27,475		30,268
Singapore [Member]
Schedule Of Geographical Segments [Line Items]
Long-lived assets	[2]	33,530				36,270				33,530		36,270		39,181
China [Member]
Schedule Of Geographical Segments [Line Items]
Long-lived assets	[2]	$ 30,849				$ 29,508				$ 30,849		$ 29,508		$ 25,689
[1]	Net sales are attributed to countries based on the location of the Company facility making the sales.
[2]	Includes net property, plant and equipment, goodwill and other intangible assets.
[3]	The change between 2016 and 2015 was attributable to the acquisition described in Note 20.

Earnings Per Share - Computatio

Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Computation of Basic Earnings per Share
Net income attributable to Stepan Company		$ 9,884	$ 21,899	$ 27,882	$ 31,913	$ 8,417	$ 21,362	$ 28,496	$ 27,916	$ 91,578	$ 86,191	$ 75,968
Weighted-average number of shares outstanding										22,946	22,793	22,730
Basic earnings per share										$ 3.99	$ 3.78	$ 3.34
Computation of Diluted Earnings per Share
Net income attributable to Stepan Company										$ 91,578	$ 86,191	$ 75,968
Weighted-average number of shares outstanding										22,946	22,793	22,730
Add weighted-average net shares related to unvested stock awards (under treasury share method)										8	6	3
Weighted-average shares applicable to diluted earnings										23,377	23,094	22,858
Diluted earnings per share		$ 0.42	$ 0.94	$ 1.19	$ 1.37	$ 0.36	$ 0.92	$ 1.24	$ 1.22	$ 3.92	$ 3.73	$ 3.32
Stock Option [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options, SARS and contingently issuable net shares related to performance stock awards (under treasury share method)	[1]									161	159	118
Stock Appreciation Rights (SARs) [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options, SARS and contingently issuable net shares related to performance stock awards (under treasury share method)										142	68	1
Performance Stock Award [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options, SARS and contingently issuable net shares related to performance stock awards (under treasury share method)										120	68	6
[1]	Options to purchase 18,630, 43,715 and 124,531 shares of common stock were not included in the computations of diluted earnings per share for the years ended December 31, 2017, 2016 and 2015, respectively. The options’ exercise prices were greater than the average market price for the common stock and the effect of the options on earnings per share would have been antidilutive.

Earnings Per Share - Computa111

Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Parenthetical) (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Options to purchase shares of common stock not included in the computations of diluted earnings per share	18,630	43,715	124,531

Accumulated Other Comprehens112

Accumulated Other Comprehensive Income (Loss) - Summary of Changes in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 634,604
Other comprehensive income before reclassifications	25,632	$ (4,639)	$ (44,161)
Amounts reclassified from AOCI	2,270	2,262	3,018
Net current period other comprehensive income	27,902	(2,377)	(41,143)
Ending Balance	740,096	634,604
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(96,775)	(88,337)	(42,914)
Other comprehensive income before reclassifications	26,214	(8,438)	(45,423)
Net current period other comprehensive income	26,214	(8,438)	(45,423)
Ending Balance	(70,561)	(96,775)	(88,337)
Defined Benefit Pension Plan Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(30,790)	(36,825)	(41,149)
Other comprehensive income before reclassifications	(582)	3,818	1,311
Amounts reclassified from AOCI	2,279	2,217	3,013
Net current period other comprehensive income	1,697	6,035	4,324
Ending Balance	(29,093)	(30,790)	(36,825)
Cash Flow Hedge Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	100	74	118
Other comprehensive income before reclassifications		(19)	(49)
Amounts reclassified from AOCI	(9)	45	5
Net current period other comprehensive income	(9)	26	(44)
Ending Balance	91	100	74
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(127,465)	(125,088)	(83,945)
Ending Balance	$ (99,563)	$ (127,465)	$ (125,088)

Accumulated Other Comprehens113

Accumulated Other Comprehensive Income (Loss) - Summary of Amounts Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income Before Provision for Income Taxes		$ 28,532	$ 29,312	$ 37,063	$ 44,330	$ 7,009	$ 27,143	$ 39,196	$ 40,468	$ 139,237	$ 113,816	$ 102,856
Tax benefit										(47,690)	(27,618)	(26,819)
Interest, net		$ (2,826)	$ (2,763)	$ (2,863)	$ (2,992)	$ (3,350)	$ (2,824)	$ (3,417)	$ (3,614)	(11,444)	(13,205)	(14,533)
Cost of Sales										1,586,742	1,427,621	1,467,926
Defined Benefit Pension Plan Adjustments [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Prior service cost	[1]									(14)	(14)	(17)
Actuarial loss	[1]									(3,509)	(3,508)	(4,757)
Income Before Provision for Income Taxes	[1],[2]									(3,523)	(3,522)	(4,774)
Tax benefit	[1]									1,244	1,305	1,761
Income applicable to common stock	[1]									(2,279)	(2,217)	(3,013)
Cash Flow Hedge Adjustments [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income Before Provision for Income Taxes	[1]									9	(73)	(13)
Tax benefit	[1]										28	8
Income applicable to common stock	[1]									9	(45)	(5)
Cash Flow Hedge Adjustments [Member] | Interest rate contracts [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Interest, net	[1]										(82)	(22)
Cash Flow Hedge Adjustments [Member] | Foreign exchange contracts [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Cost of Sales	[1]									9	9	9
Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income applicable to common stock	[1]									$ (2,270)	$ (2,262)	$ (3,018)
[1]	Amounts in parentheses denote expense to statement of income.
[2]	This component of accumulated other comprehensive income is included in the computation of net periodic benefit cost (see Note 13 for details regarding net periodic benefit costs for the Company’s U.S. and U.K. defined benefit plans).

Acquisitions - Additional Infor

Acquisitions - Additional Information (Detail)

Oct. 03, 2016USD ($)CustomerT

Jun. 15, 2015USD ($)T

Dec. 31, 2017USD ($)

Sep. 30, 2017USD ($)

Jun. 30, 2017USD ($)ft²T

Mar. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2016BRL

Sep. 30, 2016USD ($)

Jun. 30, 2016USD ($)

Mar. 31, 2016USD ($)

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Mar. 31, 2017BRL

Dec. 31, 2016BRL

Oct. 03, 2016BRLCustomerT

Business Acquisition [Line Items]

Paid from cash on hand

$ 4,339,000

$ 23,510,000

$ 5,133,000

Goodwill

$ 25,118,000

$ 25,308,000

25,118,000

25,308,000

11,265,000

Net sales

473,823,000

$ 487,814,000

$ 495,101,000

$ 468,269,000

420,636,000

$ 445,030,000

$ 454,603,000

$ 445,897,000

1,925,007,000

[1]

1,766,166,000

[1]

1,776,167,000

[1]

Net income

9,884,000

$ 21,899,000

$ 27,882,000

31,913,000

8,417,000

$ 21,362,000

$ 28,496,000

$ 27,916,000

91,578,000

86,191,000

75,968,000

Capital expenditures

$ 78,613,000

103,076,000

119,349,000

Sun Products Corporation's (SUN's) Pasadena, Texas [Member]

Business Acquisition [Line Items]

Capital expenditures

13,000,000

Acquisition of land

3,377,000

Acquisition of manufacturing assets

9,623,000

Non-compete Agreements [Member]

Business Acquisition [Line Items]

Amortization periods for the identifiable intangible assets at the time of acquisition

5 years

Minimum [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Amortization periods for the identifiable intangible assets at the time of acquisition

10 years

Maximum [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Amortization periods for the identifiable intangible assets at the time of acquisition

13 years

Brazil [Member]

Business Acquisition [Line Items]

Net sales

[1]

$ 109,960,000

74,961,000

63,439,000

Surfactants [Member]

Business Acquisition [Line Items]

Goodwill

$ 19,160,000

19,491,000

$ 19,160,000

19,491,000

5,402,000

Tebras And PBC [Member]

Business Acquisition [Line Items]

Goodwill

$ 14,207,000

Acquisition of intangible assets

7,354,000

Acquisition of property, plant and equipment

5,716,000

Acquisition of liabilities

3,487,000

Tebras And PBC [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Acquisition of intangible assets

$ 4,331,000

Amortization periods for the identifiable intangible assets at the time of acquisition

13 years

Tebras And PBC [Member] | Supply Contract [Member]

Business Acquisition [Line Items]

Acquisition of intangible assets

$ 2,555,000

Amortization periods for the identifiable intangible assets at the time of acquisition

4 years

Tebras And PBC [Member] | Non-compete Agreements [Member]

Business Acquisition [Line Items]

Acquisition of intangible assets

$ 468,000

Amortization periods for the identifiable intangible assets at the time of acquisition

5 years

Tebras And PBC [Member] | Before purchase accounting adjustments [Member]

Business Acquisition [Line Items]

Goodwill

14,327,000

Tebras And PBC [Member] | After purchase accounting adjustments [Member]

Business Acquisition [Line Items]

Goodwill

14,207,000

Tebras And PBC [Member] | Brazil [Member]

Business Acquisition [Line Items]

Net sales

28,000,000

Tebras And PBC [Member] | Brazil [Member] | Maximum [Member]

Business Acquisition [Line Items]

Net income

$ 2,000,000

Tebras And PBC [Member] | Surfactants [Member] | Brazil [Member]

Business Acquisition [Line Items]

Capacity of production facility expected to be acquired | T

25,000

25,000

Original purchase price of acquisitions

$ 29,075,000

BRL 93,309,000

Paid from cash on hand

21,812,000

BRL 70,000,000

Deposited in escrow

2,804,000

2,804,000

BRL 9,000,000

Unpaid working capital adjustments

$ 4,459,000

$ 4,459,000

BRL 14,309,000

Working capital adjustment amount paid

4,339,000

BRL 13,925,000

Adjusted purchase price of the acquisitions

$ 28,955,000

BRL 92,925,000

Tebras And PBC [Member] | Surfactants [Member] | Brazil [Member] | Minimum [Member]

Business Acquisition [Line Items]

Number of customers | Customer

1,200

1,200

Procter and Gamble Company [Member] | Brazil [Member]

Business Acquisition [Line Items]

Capacity of production facility | T

30,000

Paid from cash on hand

$ 5,133,000

Goodwill

0

Acquisition of intangible assets

0

Acquisition of property, plant and equipment

6,007,000

Acquisition of liabilities

$ 874,000

2017 Acquisition Agreement [Member] | BASF Mexicana, S.A. DE C.V. [Member] | Surfactants [Member] | Ecatepec, Mexico [Member]

Business Acquisition [Line Items]

Capacity of production facility expected to be acquired | T

50,000

Warehouse space, laboratory and office space currently expected to be acquired | ft²

124,000

[1]

Net sales are attributed to countries based on the location of the Company facility making the sales.

Acquisitions - Summary of Asset

Acquisitions - Summary of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Oct. 03, 2016	Dec. 31, 2015
Assets:
Goodwill	$ 25,118	$ 25,308		$ 11,265
Tebras And PBC [Member]
Assets:
Current assets			$ 5,165
Property, plant and equipment			5,716
Identifiable intangible assets			7,354
Goodwill			14,207
Total assets acquired			32,442
Liabilities:
Current liabilities			408
Deferred tax liability			3,079
Total liabilities assumed			3,487
Net assets acquired			$ 28,955

Sale of Product Line - Addition

Sale of Product Line - Additional Information (Detail) - USD ($)

3 Months Ended

12 Months Ended

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

[1]

Dec. 31, 2016

[1]

Dec. 31, 2015

Dec. 31, 2014

Jan. 31, 2015

Sale Of Product Line [Line Items]

Net sales

$ 473,823,000

$ 487,814,000

$ 495,101,000

$ 468,269,000

$ 420,636,000

$ 445,030,000

$ 454,603,000

$ 445,897,000

$ 1,925,007,000

$ 1,766,166,000

$ 1,776,167,000

[1]

Specialty polyurethane systems product line (kits) [Member]

Sale Of Product Line [Line Items]

Sale of product line for cash

$ 3,262,000

Net sales

$ 2,800,000

Gain from the kits sale

$ 2,862,000

[1]

Net sales are attributed to countries based on the location of the Company facility making the sales.

Business Restructuring and A117

Business Restructuring and Asset Impairments - Additional Information (Detail)	1 Months Ended	3 Months Ended			12 Months Ended
	Jun. 30, 2017Employees	Dec. 31, 2017USD ($)	Jun. 30, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2017USD ($)Employees	Dec. 31, 2016USD ($)
2017 Restructuring [Member] | Fieldsboro, NJ [Member]
Restructuring Cost And Reserve [Line Items]
Business restructuring		$ 915,000
Depreciation expense		$ 1,290,000
2017 Restructuring [Member] | Singapore [Member] | Surfactants [Member]
Restructuring Cost And Reserve [Line Items]
Number positions eliminated | Employees	11
2017 Restructuring [Member] | Singapore [Member] | Surfactants [Member] | Termination Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Business restructuring			$ 132,000		$ 0
2016 Restructuring [Member] | Longford Mills [Member]
Restructuring Cost And Reserve [Line Items]
Business restructuring					2,022,000	$ 2,817,000
2016 Restructuring [Member] | Longford Mills [Member] | Termination Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Business restructuring						1,594,000
2016 Restructuring [Member] | Longford Mills [Member] | Other Expense [Member]
Restructuring Cost And Reserve [Line Items]
Business restructuring					2,022,000	1,223,000
2016 Restructuring [Member] | Longford Mills [Member] | Surfactants [Member]
Restructuring Cost And Reserve [Line Items]
Business restructuring					4,839,000
Depreciation expense					$ 0	4,471,000
Number positions eliminated | Employees					30
Decommissioning expense					$ 2,022,000
2016 Restructuring [Member] | Longford Mills [Member] | Surfactants [Member] | Termination Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Business restructuring					1,594,000
2016 Restructuring [Member] | Longford Mills [Member] | Surfactants [Member] | Other Expense [Member]
Restructuring Cost And Reserve [Line Items]
Business restructuring					$ 3,245,000
2016 Asset Impairments [Member] | Surfactants [Member]
Restructuring Cost And Reserve [Line Items]
Asset impairment charges				$ 4,247,000
2016 Asset Impairments [Member] | United States [Member] | Nonionic Surfactants [Member]
Restructuring Cost And Reserve [Line Items]
Asset impairment charges				2,297,000
2016 Asset Impairments [Member] | Brazil [Member] | Bahia Plant
Restructuring Cost And Reserve [Line Items]
Asset impairment charges				$ 1,950,000
2016 Asset Impairments [Member] | Brazil [Member] | Bahia Plant | Take-Or-Pay Contract [Member] | Net Sales [Member]
Restructuring Cost And Reserve [Line Items]
Compensation for lost future revenues						$ 4,250,000

Business Restructuring and A118

Business Restructuring and Asset Impairments - Reconciliation of Restructuring Liability (Detail) - 2016 Restructuring [Member] - Longford Mills [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost And Reserve [Line Items]
Restructuring liability	$ 1,985
Expense recognized	2,022	$ 2,817
Amounts paid	(3,389)	(781)
Foreign currency translation	73	(51)
Restructuring liability	691	1,985
Termination Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring liability	1,548
Expense recognized		1,594
Amounts paid	(1,012)
Foreign currency translation	56	(46)
Restructuring liability	592	1,548
Other Expense [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring liability	437
Expense recognized	2,022	1,223
Amounts paid	(2,377)	(781)
Foreign currency translation	17	(5)
Restructuring liability	$ 99	$ 437

Customer Claims - Additional In

Customer Claims - Additional Information (Detail) - Surfactants [Member]	3 Months Ended		12 Months Ended
	Dec. 31, 2017USD ($)Claim	Dec. 31, 2016Claim	Dec. 31, 2016USD ($)
Loss Contingencies [Line Items]
Number of customer claims | Claim		2
Insurance claims reserve amount			$ 7,367,000
Claim paid	$ 2,709,000
Number of claims and reversed | Claim	1
Claims and reversed remainder of claim realizing income	$ 4,660,000

Statement of Cash Flows - No120

Statement of Cash Flows - Noncash Investing and Financing Activities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Elements [Line Items]
Noncash investing activities incurred for fixed asset acquisitions	$ 12,600,000	$ 10,410,000	$ 9,515,000
Common Stock [Member] | Stock Award Plan [Member]
Supplemental Cash Flow Elements [Line Items]
Noncash financing activities shares issued	35,372
Noncash financing activities issued value	$ 2,941,000
Tebras And PBC [Member]
Supplemental Cash Flow Elements [Line Items]
Noncash investing activities unpaid working capital adjustments related to 2016 acquisitions		$ 4,459,000

TIORCO, LLC Joint Venture - Add

TIORCO, LLC Joint Venture - Additional Information (Detail) - TIORCO LLC [Member] - USD ($)	3 Months Ended
	Dec. 31, 2015	Mar. 31, 2016
Schedule Of Equity Method Investments [Line Items]
Company’s share of exit costs upon dissolution	$ 2,356,000
Cash investment		$ 2,900,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($)	Jan. 30, 2018	Dec. 31, 2017	Jul. 10, 2015	Jun. 27, 2013	Sep. 29, 2005
Multi currency revolving credit agreement [Member]
Subsequent Event [Line Items]
Revolving credit agreement		$ 125,000,000
Credit agreement secured date		Jul. 10, 2019
Series 2005-A Senior Notes Due November 1, 2018 [Member]
Subsequent Event [Line Items]
Aggregate principal amount					$ 40,000,000
Debt instrument interest rate percentage					5.69%
Series 2010-A Senior Notes Due June 1, 2022 [Member]
Subsequent Event [Line Items]
Aggregate principal amount					$ 40,000,000
Debt instrument interest rate percentage					5.88%
Series 2011-A Senior Notes Due November 1, 2023 [Member]
Subsequent Event [Line Items]
Aggregate principal amount					$ 65,000,000
Debt instrument interest rate percentage					4.86%
Senior Notes Due June 27, 2025 [Member]
Subsequent Event [Line Items]
Aggregate principal amount				$ 100,000,000
Debt instrument interest rate percentage				3.86%
Senior Notes Due July 10, 2027 [Member]
Subsequent Event [Line Items]
Aggregate principal amount			$ 100,000,000
Debt instrument interest rate percentage			3.95%
Subsequent Event [Member] | Multi currency revolving credit agreement [Member]
Subsequent Event [Line Items]
Revolving credit agreement	$ 350,000,000
Credit agreement secured date	Jan. 30, 2023
Subsequent Event [Member] | Credit Agreement [Member] | Multi currency revolving credit agreement [Member]
Subsequent Event [Line Items]
Revolving credit agreement	$ 350,000,000
Credit agreement secured date	Jan. 30, 2023
Facility term	5 years

Selected Quarterly Financial123

Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Net Sales	$ 473,823	$ 487,814	$ 495,101	$ 468,269	$ 420,636	$ 445,030	$ 454,603	$ 445,897	$ 1,925,007	[1]	$ 1,766,166	[1]	$ 1,776,167	[1]
Gross Profit	80,599	75,602	89,966	92,098	68,720	83,395	92,931	93,499	338,265		338,545		308,241
Operating income	30,831	30,309	38,961	46,059	9,932	28,738	42,916	44,607	146,160		126,193		122,790
Interest, net	(2,826)	(2,763)	(2,863)	(2,992)	(3,350)	(2,824)	(3,417)	(3,614)	(11,444)		(13,205)		(14,533)
Income Before Income Taxes	28,532	29,312	37,063	44,330	7,009	27,143	39,196	40,468	139,237		113,816		102,856
Net Income	9,886	21,853	27,896	31,912	8,411	21,367	28,501	27,919	91,547		86,198		76,037
Net income attributable to Stepan Company	$ 9,884	$ 21,899	$ 27,882	$ 31,913	$ 8,417	$ 21,362	$ 28,496	$ 27,916	$ 91,578		$ 86,191		$ 75,968
Diluted earnings per share	$ 0.42	$ 0.94	$ 1.19	$ 1.37	$ 0.36	$ 0.92	$ 1.24	$ 1.22	$ 3.92		$ 3.73		$ 3.32
[1]	Net sales are attributed to countries based on the location of the Company facility making the sales.