Summary of Significant Accounting Policies (Policies)	12 Months Ended
Dec. 31, 2012
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation: The consolidated financial statements include the accounts of West Pharmaceutical Services, Inc. and its majority-owned subsidiaries (which may be referred to as “West”, the “Company”, “we”, “us” or “our”) after the elimination of intercompany transactions. We have no participation or other rights in variable interest entities.
Reclassifications	Reclassifications: Certain reclassifications were made to prior period financial statements to conform to the current year presentation.
Use of Estimates	Use of Estimates: The financial statements are prepared in conformity with U.S. GAAP. These principles require management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingencies in the financial statements. Actual amounts realized may differ from these estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents: Cash equivalents include time deposits, certificates of deposit and all highly liquid debt instruments with maturities of three months or less at the time of purchase.
Accounts Receivable	Accounts Receivable: Our accounts receivable balance was net of an allowance for doubtful accounts of $0.5 million and $0.3 million at December 31, 2012 and 2011, respectively. We record the allowance based on a specific identification methodology.
Inventories	Inventories: Inventories are valued at the lower of standard cost (which approximates actual cost on a first-in-first-out basis) or market.
Property, Plant and Equipment	Property, Plant and Equipment: Property, plant and equipment assets are carried at cost. Maintenance and minor repairs and renewals are charged to expense as incurred. Costs incurred for computer software developed or obtained for internal use are capitalized for application development activities and immediately expensed for preliminary project activities or post-implementation activities. Upon sale or retirement of depreciable assets, costs and related accumulated depreciation are eliminated, and gains or losses are recognized in restructuring and other items. Depreciation and amortization are computed principally using the straight-line method over the estimated useful lives of the assets, or the remaining term of the lease, if shorter.
Impairment of Goodwill and Other Intangible Assets	Impairment of Goodwill and Other Intangible Assets: Goodwill and indefinite-lived intangibles are tested for impairment at least annually, following the completion of our annual budget and long-range planning process, or whenever circumstances indicate that the carrying value of these assets may not be recoverable. Goodwill is tested for impairment as part of the reporting unit to which it belongs. Our reporting units are the same as, or one level below, our operating segments. The goodwill impairment test first requires a comparison of the fair value of each reporting unit to its carrying amount, including goodwill. If the carrying amount exceeds fair value, a second step must be performed. The second step requires the comparison of the carrying amount of the goodwill to its implied fair value, which is calculated as if the reporting unit had just been acquired as of the testing date. Any excess of the carrying amount of goodwill over the implied fair value would represent an impairment loss. Certain trademarks and in-process R&D have been determined to have indefinite lives and, therefore, are not subject to amortization. Impairment testing for indefinite-lived intangible assets requires a comparison between the fair value and carrying value of the asset, and any excess carrying value would represent an impairment. Fair values are determined using discounted cash flow analyses. Intangible assets with finite lives are amortized using the straight-line method over their estimated useful lives of 5 to 25 years, and reviewed for recovery whenever circumstances indicate that the carrying value of these assets may not be recoverable.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets: Long-lived assets, including property, plant and equipment, are tested for impairment whenever circumstances indicate that the carrying value of these assets may not be recoverable. An asset is considered impaired if the carrying value of the asset exceeds the sum of the future expected undiscounted cash flows to be derived from the asset. Once an asset is considered impaired, an impairment loss is recorded within restructuring and other items for the difference between the asset's carrying value and its fair value. For assets held and used in the business, management determines fair value using estimated future cash flows to be derived from the asset, discounted to a net present value using an appropriate discount rate. For assets held for sale or for investment purposes, management determines fair value by estimating the proceeds to be received upon sale of the asset, less disposition costs.
Employee Benefits	Employee Benefits: The measurement of the obligations under our defined benefit pension and postretirement medical plans are subject to a number of assumptions. These include the rate of return on plan assets (for funded plans) and the rate at which the future obligations are discounted to present value. U.S. GAAP requires the recognition of an asset or liability for the funded status of a defined benefit postretirement plan, as measured by the difference between the fair value of plan assets, if any, and the benefit obligation. For a pension plan, the benefit obligation is the projected benefit obligation; for any other postretirement plan, such as a retiree health plan, the benefit obligation is the accumulated postretirement benefit obligation. See Note 14, Benefit Plans, for a more detailed discussion of our pension and other retirement plans.
Financial Instruments	Financial Instruments: All derivatives are recognized as either assets or liabilities in the balance sheet and recorded at their fair value. For a derivative designated as hedging the exposure to variable cash flows of a forecasted transaction (referred to as a cash flow hedge), the effective portion of the derivative's gain or loss is initially reported as a component of other comprehensive income, net of tax, and subsequently reclassified into earnings when the forecasted transaction affects earnings. For a derivative designated as hedging the exposure to changes in the fair value of a recognized asset or liability or a firm commitment (referred to as a fair value hedge), the derivative's gain or loss is recognized in earnings in the period of change together with the offsetting loss or gain on the hedged item. For a derivative designated as hedging the foreign currency exposure of a net investment in a foreign operation, the gain or loss is reported in other comprehensive income, net of tax, as part of the cumulative translation adjustment. The ineffective portion of any derivative used in a hedging transaction is recognized immediately into earnings. Derivative financial instruments that are not designated as hedges are also recorded at fair value, with the change in fair value recognized immediately into earnings. We do not purchase or hold any derivative financial instrument for investment or trading purposes.
Foreign Currency Translation	Foreign Currency Translation: Foreign currency transaction gains and losses are recognized in the determination of net income. Foreign currency translation adjustments of subsidiaries and affiliates operating outside of the United States are accumulated in other comprehensive income, a separate component of equity.
Revenue Recognition	Revenue Recognition: Revenue is recognized when persuasive evidence of a sales arrangement exists, title and risk of loss have transferred, the selling price is fixed or determinable, and collectability is reasonably assured. Generally, sales are recognized upon shipment or upon delivery to our customers' site, based upon shipping terms or legal requirements. Some customers receive pricing rebates upon attaining established sales volumes. We record rebate costs when sales occur based on our assessment of the likelihood that the required volumes will be attained. We also establish product return liabilities for customer quality claims, as we believe that we are able to reasonably estimate the amount of returns based on our substantial historical experience.
Shipping and Handling Costs	Shipping and Handling Costs: Shipping and handling costs are included in cost of goods and services sold. Shipping and handling costs billed to customers in connection with the sale are included in net sales.
Research and Development	Research and Development: Research and development expenditures are for the creation, engineering and application of new or improved products and processes. Expenditures include primarily salaries and outside services for those directly involved in research and development activities and are expensed as incurred.
Environmental Remediation and Compliance Costs	Environmental Remediation and Compliance Costs: Environmental remediation costs are accrued when such costs are probable and reasonable estimates are determinable. Cost estimates include investigation, cleanup and monitoring activities; such estimates are adjusted, if necessary, based on additional findings. Environmental compliance costs are expensed as incurred as part of normal operations.
Litigation	Litigation: From time to time, we are involved in product liability matters and other legal proceedings and claims generally incidental to our normal business activities. In accordance with U.S. GAAP, we accrue for loss contingencies when it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. These estimates are based on an analysis made by internal and external legal counsel considering information known at the time. Legal costs in connection with loss contingencies are expensed as incurred.
Income Taxes	Income Taxes: Deferred income taxes are recognized by applying enacted statutory tax rates, applicable to future years, to temporary differences between the tax basis and financial statement carrying values of our assets and liabilities. Valuation allowances are established when it is more likely than not that all or a portion of a deferred tax asset will not be realized. No provision is made for the U.S. income taxes on the undistributed earnings of wholly-owned foreign subsidiaries as such earnings are intended to be permanently reinvested. We recognize interest costs related to income taxes in interest expense and penalties within restructuring and other items. The tax law ordering approach is used for purposes of determining whether an excess tax benefit has been realized during the year.
Stock-based Compensation	Stock-Based Compensation: Under the fair value provisions of U.S. GAAP, stock-based compensation cost is measured at the grant date based on the value of the award and is recognized as expense over the vesting period. In order to determine the fair value of stock options on the grant date, the company uses the Black-Scholes valuation model.
Net Income Per Share	Net Income Per Share: Basic net income per share is computed by dividing net income attributable to common shareholders by the weighted average number of shares of common stock outstanding during each period. Net income per share assuming dilution considers the dilutive effect of outstanding stock options and other stock awards based on the treasury stock method, as well as convertible debt based on the if-converted method. The treasury stock method assumes the use of exercise proceeds to repurchase common stock at the average fair market value in the period. The if-converted method assumes conversion of the debt at the beginning of the reporting period (or at time of issuance, if later). In addition, interest charges applicable to the convertible debt, net of tax, are added back to net income for the purpose of this calculation.
Recently Adopted Standards	Recently Adopted Standards In September 2011, the Financial Accounting Standards Board (“FASB”) issued guidance for the impairment testing of goodwill. The guidance permits an entity to first assess qualitative factors to determine whether it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform the two-step goodwill impairment test. We adopted this guidance as of January 1, 2012, and considered it when performing our annual goodwill impairment test. The adoption of this guidance did not have an impact on our financial statements. In May 2011, the FASB issued guidance to provide a consistent definition of fair value and ensure that the fair value measurement and disclosure requirements are similar between U.S. GAAP and International Financial Reporting Standards. It also changes certain fair value measurement principles and expands the disclosures for fair value measurements that are estimated using significant unobservable inputs. We adopted this guidance as of January 1, 2012, on a prospective basis. The adoption of this guidance did not have a material impact on our financial statements. Please refer to Note 13, Fair Value Measurements, for additional details.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2012

Principles of Consolidation: The consolidated financial statements include the accounts of West Pharmaceutical Services, Inc. and its majority-owned subsidiaries (which may be referred to as “West”, the “Company”, “we”, “us” or “our”) after the elimination of intercompany transactions. We have no participation or other rights in variable interest entities.

Reclassifications

Reclassifications: Certain reclassifications were made to prior period financial statements to conform to the current year presentation.

Use of Estimates

Use of Estimates: The financial statements are prepared in conformity with U.S. GAAP. These principles require management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingencies in the financial statements. Actual amounts realized may differ from these estimates.

Cash and Cash Equivalents

Cash and Cash Equivalents: Cash equivalents include time deposits, certificates of deposit and all highly liquid debt instruments with maturities of three months or less at the time of purchase.

Accounts Receivable

Accounts Receivable: Our accounts receivable balance was net of an allowance for doubtful accounts of $0.5 million and $0.3 million at December 31, 2012 and 2011, respectively. We record the allowance based on a specific identification methodology.

Inventories

Inventories: Inventories are valued at the lower of standard cost (which approximates actual cost on a first-in-first-out basis) or market.

Property, Plant and Equipment

Property, Plant and Equipment: Property, plant and equipment assets are carried at cost. Maintenance and minor repairs and renewals are charged to expense as incurred. Costs incurred for computer software developed or obtained for internal use are capitalized for application development activities and immediately expensed for preliminary project activities or post-implementation activities. Upon sale or retirement of depreciable assets, costs and related accumulated depreciation are eliminated, and gains or losses are recognized in restructuring and other items. Depreciation and amortization are computed principally using the straight-line method over the estimated useful lives of the assets, or the remaining term of the lease, if shorter.

Impairment of Goodwill and Other Intangible Assets

Impairment of Goodwill and Other Intangible Assets: Goodwill and indefinite-lived intangibles are tested for impairment at least annually, following the completion of our annual budget and long-range planning process, or whenever circumstances indicate that the carrying value of these assets may not be recoverable. Goodwill is tested for impairment as part of the reporting unit to which it belongs. Our reporting units are the same as, or one level below, our operating segments. The goodwill impairment test first requires a comparison of the fair value of each reporting unit to its carrying amount, including goodwill. If the carrying amount exceeds fair value, a second step must be performed. The second step requires the comparison of the carrying amount of the goodwill to its implied fair value, which is calculated as if the reporting unit had just been acquired as of the testing date. Any excess of the carrying amount of goodwill over the implied fair value would represent an impairment loss.

Certain trademarks and in-process R&D have been determined to have indefinite lives and, therefore, are not subject to amortization. Impairment testing for indefinite-lived intangible assets requires a comparison between the fair value and carrying value of the asset, and any excess carrying value would represent an impairment. Fair values are determined using discounted cash flow analyses.

Intangible assets with finite lives are amortized using the straight-line method over their estimated useful lives of 5 to 25 years, and reviewed for recovery whenever circumstances indicate that the carrying value of these assets may not be recoverable.

Impairment of Long-Lived Assets

Impairment of Long-Lived Assets: Long-lived assets, including property, plant and equipment, are tested for impairment whenever circumstances indicate that the carrying value of these assets may not be recoverable. An asset is considered impaired if the carrying value of the asset exceeds the sum of the future expected undiscounted cash flows to be derived from the asset. Once an asset is considered impaired, an impairment loss is recorded within restructuring and other items for the difference between the asset's carrying value and its fair value. For assets held and used in the business, management determines fair value using estimated future cash flows to be derived from the asset, discounted to a net present value using an appropriate discount rate. For assets held for sale or for investment purposes, management determines fair value by estimating the proceeds to be received upon sale of the asset, less disposition costs.

Employee Benefits

Employee Benefits: The measurement of the obligations under our defined benefit pension and postretirement medical plans are subject to a number of assumptions. These include the rate of return on plan assets (for funded plans) and the rate at which the future obligations are discounted to present value. U.S. GAAP requires the recognition of an asset or liability for the funded status of a defined benefit postretirement plan, as measured by the difference between the fair value of plan assets, if any, and the benefit obligation. For a pension plan, the benefit obligation is the projected benefit obligation; for any other postretirement plan, such as a retiree health plan, the benefit obligation is the accumulated postretirement benefit obligation. See Note 14, Benefit Plans, for a more detailed discussion of our pension and other retirement plans.

Financial Instruments

Financial Instruments: All derivatives are recognized as either assets or liabilities in the balance sheet and recorded at their fair value. For a derivative designated as hedging the exposure to variable cash flows of a forecasted transaction (referred to as a cash flow hedge), the effective portion of the derivative's gain or loss is initially reported as a component of other comprehensive income, net of tax, and subsequently reclassified into earnings when the forecasted transaction affects earnings. For a derivative designated as hedging the exposure to changes in the fair value of a recognized asset or liability or a firm commitment (referred to as a fair value hedge), the derivative's gain or loss is recognized in earnings in the period of change together with the offsetting loss or gain on the hedged item. For a derivative designated as hedging the foreign currency exposure of a net investment in a foreign operation, the gain or loss is reported in other comprehensive income, net of tax, as part of the cumulative translation adjustment. The ineffective portion of any derivative used in a hedging transaction is recognized immediately into earnings. Derivative financial instruments that are not designated as hedges are also recorded at fair value, with the change in fair value recognized immediately into earnings. We do not purchase or hold any derivative financial instrument for investment or trading purposes.

Foreign Currency Translation

Foreign Currency Translation: Foreign currency transaction gains and losses are recognized in the determination of net income. Foreign currency translation adjustments of subsidiaries and affiliates operating outside of the United States are accumulated in other comprehensive income, a separate component of equity.

Revenue Recognition

Revenue Recognition: Revenue is recognized when persuasive evidence of a sales arrangement exists, title and risk of loss have transferred, the selling price is fixed or determinable, and collectability is reasonably assured. Generally, sales are recognized upon shipment or upon delivery to our customers' site, based upon shipping terms or legal requirements. Some customers receive pricing rebates upon attaining established sales volumes. We record rebate costs when sales occur based on our assessment of the likelihood that the required volumes will be attained. We also establish product return liabilities for customer quality claims, as we believe that we are able to reasonably estimate the amount of returns based on our substantial historical experience.

Shipping and Handling Costs

Shipping and Handling Costs: Shipping and handling costs are included in cost of goods and services sold. Shipping and handling costs billed to customers in connection with the sale are included in net sales.

Research and Development

Research and Development: Research and development expenditures are for the creation, engineering and application of new or improved products and processes. Expenditures include primarily salaries and outside services for those directly involved in research and development activities and are expensed as incurred.

Environmental Remediation and Compliance Costs

Environmental Remediation and Compliance Costs: Environmental remediation costs are accrued when such costs are probable and reasonable estimates are determinable. Cost estimates include investigation, cleanup and monitoring activities; such estimates are adjusted, if necessary, based on additional findings. Environmental compliance costs are expensed as incurred as part of normal operations.

Litigation

Litigation: From time to time, we are involved in product liability matters and other legal proceedings and claims generally incidental to our normal business activities. In accordance with U.S. GAAP, we accrue for loss contingencies when it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. These estimates are based on an analysis made by internal and external legal counsel considering information known at the time. Legal costs in connection with loss contingencies are expensed as incurred.

Income Taxes

Income Taxes: Deferred income taxes are recognized by applying enacted statutory tax rates, applicable to future years, to temporary differences between the tax basis and financial statement carrying values of our assets and liabilities. Valuation allowances are established when it is more likely than not that all or a portion of a deferred tax asset will not be realized. No provision is made for the U.S. income taxes on the undistributed earnings of wholly-owned foreign subsidiaries as such earnings are intended to be permanently reinvested. We recognize interest costs related to income taxes in interest expense and penalties within restructuring and other items. The tax law ordering approach is used for purposes of determining whether an excess tax benefit has been realized during the year.

Stock-based Compensation

Stock-Based Compensation: Under the fair value provisions of U.S. GAAP, stock-based compensation cost is measured at the grant date based on the value of the award and is recognized as expense over the vesting period. In order to determine the fair value of stock options on the grant date, the company uses the Black-Scholes valuation model.

Net Income Per Share

Net Income Per Share: Basic net income per share is computed by dividing net income attributable to common shareholders by the weighted average number of shares of common stock outstanding during each period. Net income per share assuming dilution considers the dilutive effect of outstanding stock options and other stock awards based on the treasury stock method, as well as convertible debt based on the if-converted method. The treasury stock method assumes the use of exercise proceeds to repurchase common stock at the average fair market value in the period. The if-converted method assumes conversion of the debt at the beginning of the reporting period (or at time of issuance, if later). In addition, interest charges applicable to the convertible debt, net of tax, are added back to net income for the purpose of this calculation.

Recently Adopted Standards

In September 2011, the Financial Accounting Standards Board (“FASB”) issued guidance for the impairment testing of goodwill. The guidance permits an entity to first assess qualitative factors to determine whether it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform the two-step goodwill impairment test. We adopted this guidance as of January 1, 2012, and considered it when performing our annual goodwill impairment test. The adoption of this guidance did not have an impact on our financial statements.

In May 2011, the FASB issued guidance to provide a consistent definition of fair value and ensure that the fair value measurement and disclosure requirements are similar between U.S. GAAP and International Financial Reporting Standards. It also changes certain fair value measurement principles and expands the disclosures for fair value measurements that are estimated using significant unobservable inputs. We adopted this guidance as of January 1, 2012, on a prospective basis. The adoption of this guidance did not have a material impact on our financial statements. Please refer to Note 13, Fair Value Measurements, for additional details.