Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2017
Accounting Policies [Abstract]
Nature of Business	Nature of Business. Silgan Holdings Inc., or Silgan, and its subsidiaries conduct business in three market segments: metal containers, closures and plastic containers. Our metal container business is engaged in the manufacture and sale of steel and aluminum containers for human and pet food and general line products. Our closures business manufactures and sells metal and plastic closures and dispensing systems for food, beverage, health care, garden, personal care, home and beauty products. Our plastic container business manufactures and sells custom designed plastic containers for personal care, food, health care, pharmaceutical, household and industrial chemical, pet care, agricultural, automotive and marine chemical products. Our metal container business has operating facilities in North America, Europe and Asia. Our closures business has operating facilities in North and South America, Europe and Asia. Our plastic container business is based in North America.
Basis of Presentation	Basis of Presentation. The consolidated financial statements include the accounts of Silgan and our subsidiaries. Newly acquired subsidiaries have been included in the consolidated financial statements from their dates of acquisition. All significant intercompany transactions have been eliminated. The preparation of consolidated financial statements in conformity with U.S. generally accepted accounting principles, or GAAP, requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results may differ from those estimates. Deferred income taxes as of December 31, 2016 previously included in other liabilities have been presented as a separate line item on the Consolidated Balance Sheet to conform to current period presentation. Stock Split. On May 3, 2017, our Board of Directors declared a two-for-one stock split of our issued common stock. The stock split was effected on May 26, 2017 in the form of a stock dividend. Stockholders of record at the close of business on May 15, 2017 were issued one additional share of common stock for each share of common stock owned on that date. Information pertaining to the number of shares outstanding, per share amounts and stock compensation has been retroactively adjusted in the accompanying financial statements and related footnotes to reflect this stock split for all periods presented, except for the Consolidated Balance Sheets and Statements of Stockholders’ Equity. Stockholders’ equity reflects the stock split by reclassifying from paid-in capital to common stock an amount equal to the par value of the additional shares issued as a result of the stock split.
Foreign Currency Transactions and Translations Policy	Generally, our subsidiaries that operate outside the United States use their local currency as the functional currency. The principal functional currency for our foreign operations is the Euro. Balance sheet accounts of our foreign subsidiaries are translated at exchange rates in effect at the balance sheet date, while revenue and expense accounts are translated at average rates prevailing during the year. Translation adjustments are reported as a component of accumulated other comprehensive loss. Gains or losses resulting from transactions denominated in foreign currencies that are not designated as a hedge are included in selling, general and administrative expenses in our Consolidated Statements of Income.
Cash and Cash Equivalents	Cash and Cash Equivalents. Cash equivalents represent short-term, highly liquid investments which are readily convertible to cash and have maturities of three months or less at the time of purchase. As a result of our cash management system, checks issued for payment may create negative book balances. Checks outstanding in excess of related book balances are included in trade accounts payable in our Consolidated Balance Sheets. Changes in outstanding checks are included in financing activities in our Consolidated Statements of Cash Flows to treat them as, in substance, cash advances.
Inventories	Inventories. Inventories are valued at the lower of cost or market (net realizable value). Cost for domestic inventories for our metal container business and certain portions of our closures business is principally determined on the last-in, first-out basis, or LIFO. Cost for inventories for our plastic container business and certain portions of our closures business is principally determined on the first-in, first-out basis, or FIFO. Cost for foreign inventories for our metal container business and certain portions of our closures business is principally determined on the average cost method.
Property, Plant and Equipment, Net	Property, Plant and Equipment, Net. Property, plant and equipment, net is stated at historical cost less accumulated depreciation. Major renewals and betterments that extend the life of an asset are capitalized and repairs and maintenance expenditures are charged to expense as incurred. Design and development costs for molds, dies and other tools that we do not own and that will be used to produce products that will be sold under long-term supply arrangements are capitalized. Depreciation is computed using the straight-line method over the estimated useful lives of depreciable assets. The principal estimated useful lives are 35 years for buildings and range between 3 years to 20 years for machinery and equipment. Leasehold improvements are amortized over the shorter of the life of the related asset or the life of the lease.
Goodwill and Other Intangible Assets, Net	Goodwill and Other Intangible Assets, Net. We review goodwill and other indefinite-lived intangible assets for impairment as of July 1 of each year and more frequently if circumstances indicate a possible impairment. We determined that goodwill and other indefinite-lived intangible assets were not impaired in our annual assessment performed during the third quarter. Definite-lived intangible assets are amortized over their estimated useful lives on a straight-line basis. Customer relationships have a weighted average life of approximately 20 years. Other definite-lived intangible assets consist primarily of a trade name and technology know-how and have a weighted average life of approximately 8 years.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets. We assess long-lived assets, including intangible assets with definite lives, for impairment whenever events or changes in circumstances indicate the carrying amount of the assets may not be fully recoverable. An impairment exists if the estimate of future undiscounted cash flows generated by the assets is less than the carrying value of the assets. If impairment is determined to exist, any related impairment loss is then measured by comparing the fair value of the assets to their carrying amount.
Hedging Instruments	Hedging Instruments. All derivative financial instruments are recorded in the Consolidated Balance Sheets at their fair values. Changes in fair values of derivatives are recorded in each period in earnings or other comprehensive loss, depending on whether a derivative is designated as part of a qualifying hedge transaction and, if it is, the type of hedge transaction. We have historically utilized certain derivative financial instruments to manage a portion of our interest rate exposure and currently utilize certain derivative financial instruments to manage a portion of our natural gas cost exposure. We do not engage in trading or other speculative uses of these financial instruments. For a financial instrument to qualify as a hedge, we must be exposed to interest rate or price risk, and the financial instrument must reduce the exposure and be designated as a hedge. Financial instruments qualifying for hedge accounting must maintain a high correlation between the hedging instrument and the item being hedged, both at inception and throughout the hedged period. We utilize certain internal hedging strategies to minimize our foreign currency exchange rate risk. Net investment hedges that qualify for hedge accounting result in the recognition of foreign currency gains or losses, net of tax, in accumulated other comprehensive loss. We generally do not utilize external derivative financial instruments to manage our foreign currency exchange rate risk.
Income Taxes	Income Taxes. We account for income taxes using the liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period of enactment of such change. No provision is made for U.S. income taxes applicable to undistributed earnings of foreign subsidiaries that are indefinitely reinvested.
Revenue Recognition	Revenue Recognition. Revenues are recognized when goods are shipped and the title and risk of loss pass to the customer. For those sites where we operate within the customer’s facilities, title and risk of loss pass to the customer upon delivery of product to clearly delineated areas within the common facility, at which time we recognize revenues. Shipping and handling fees and costs incurred in connection with products sold are recorded in cost of goods sold in our Consolidated Statements of Income.
Stock-Based Compensation	Stock-Based Compensation. We currently have one stock-based compensation plan in effect under which we have issued stock options and restricted stock units to our officers, other key employees and outside directors. A restricted stock unit represents the right to receive one share of our common stock at a future date. Unvested restricted stock units that have been issued do not have voting rights and may not be disposed of or transferred during the vesting period.
New Accounting Pronouncements	Recently Adopted Accounting Pronouncements. In January 2017, the Financial Accounting Standards Board, or the FASB, issued an accounting standards update, or ASU, that provides guidance to simplify the test for goodwill impairment. This guidance eliminates the requirement to assign the fair value of a reporting unit to each of its assets and liabilities to quantify a goodwill impairment charge. Under this amended guidance, the goodwill impairment charge to be recognized will be determined based on comparing the carrying value of the reporting unit to its fair value. As permitted, we have adopted this amendment early in conjunction with our annual assessment of goodwill as of July 1, 2017 and have applied it prospectively. The adoption of this amendment did not have any effect on our financial position, results of operations or cash flows. In August 2017, the FASB issued an ASU that (i) amends the hedge accounting recognition and presentation requirements to better portray the economic results of an entity's risk management activities in its financial statements and (ii) simplifies the application of hedge accounting guidance under GAAP. This amendment requires an entity to present the earnings effect of the hedging instrument in the same income line item in which the earnings effect of the hedged item is reported. As permitted, we have adopted this amendment early, effective January 1, 2017, using a modified retrospective approach. The adoption of this amendment did not have any effect on our financial position, results of operations or cash flows. In February 2018, the FASB issued an ASU that provides for the reclassification of stranded tax effects resulting from the decrease in the federal corporate tax rate and certain other tax effects as a result of the recently enacted legislation in the United States commonly referred to as the Tax Cuts and Jobs Act, or the 2017 Tax Act, from accumulated other comprehensive loss to retained earnings. As permitted, we have adopted this amendment early, effective December 31, 2017. As a result of this amendment, we increased each of accumulated other comprehensive loss and retained earnings by $22.1 million. See Note 4 for further information. Recently Issued Accounting Pronouncements. In May 2014, the FASB issued an ASU that amends the guidance for revenue recognition. This amendment contains principles that will require an entity to recognize revenue to depict the transfer of goods and services to customers at an amount that an entity expects to be entitled to in exchange for those goods or services. We will adopt this amendment on January 1, 2018, using the modified retrospective method. The adoption of this amendment will require us to accelerate the recognition of revenue as compared to the current standards for certain customers in cases where we produce products with no alternative use to us and for which we have an enforceable right of payment for production completed to date. We do not expect that this amendment will have a material impact on our financial position, results of operations or cash flows. In February 2016, the FASB issued an ASU that amends existing guidance for certain leases by lessees. This amendment will require us to recognize assets and liabilities on the balance sheet for the rights and obligations created by long-term leases and to disclose additional quantitative and qualitative information about leasing arrangements. In addition, this amendment clarifies the presentation requirements of the effects of leases in the statement of income and statement of cash flows. This amendment will be effective for us on January 1, 2019. Early adoption is permitted. This amendment is required to be adopted using a modified retrospective approach. We are currently evaluating the impact of this amendment on our financial position, results of operations and cash flows. In August 2016, the FASB issued an ASU that provides guidance for cash flow classification for certain cash receipts and cash payments to address diversity in practice in the manner in which items are classified on the statement of cash flows as either operating, investing or financing activities. This amendment will be effective for us on January 1, 2018. This amendment is required to be adopted using a retrospective approach and is not expected to have a material impact on our statement of cash flows. In March 2017, the FASB issued an ASU that amends the presentation of net periodic pension cost and net periodic postretirement benefit cost. This amendment will require an entity to disaggregate the service cost component from the other components of net periodic benefit cost, to report the service cost component in the same line item as other compensation costs and to report the other components of net periodic benefit cost (which include interest cost, expected return on plan assets, amortization of prior service cost or credit and actuarial gains and losses) separately. In addition, capitalization of net periodic benefit cost in assets will be limited to the service cost component. We will adopt this amendment on January 1, 2018. This amendment is required to be adopted (i) retrospectively with respect to the disaggregation of the service cost component from the other components of net periodic benefit cost and the separate reporting of the other components of net periodic benefit cost and (ii) prospectively with respect to the capitalization in assets of the service cost component. We do not expect that this amendment will have a material impact on our financial position, results of operations or cash flows.