Stock-Based Compensation	6 Months Ended
Jun. 30, 2026
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation The West Pharmaceutical Services, Inc. 2016 Omnibus Incentive Compensation Plan (the “2016 Plan”) provides for the granting of stock options, stock appreciation rights ("SARs"), restricted stock awards and performance awards to employees and non-employee directors. A committee of the Board of Directors determines the terms and conditions of awards to be granted. Vesting requirements vary by award. In March 2025, the Board of Directors approved, and our stockholders subsequently approved in May 2025, an amendment to the 2016 Plan ("the Amended and Restated 2016 Plan"), which, among other things, added 2.0 million shares of common stock to the maximum number of shares of common stock as to which awards may be granted. Following the approval of the Amended and Restated 2016 Plan, all stock options or SARs that are not forfeited or cancelled will reduce the number of shares available for issuance under the Amended and Restated 2016 Plan by one share for each share subject to the award. Awards issued following the amendment that are payable in common stock (other than stock options or SARs) will reduce the total number of shares available for grant under the Amended and Restated 2016 Plan by an amount equal to 2.0 times the number of shares subject to the award. The reduction was previously equal to 2.5 times the number of shares subject to the award under the 2016 Plan. At June 30, 2026, there were approximately 2.8 million shares remaining in the Amended and Restated 2016 Plan for future grants. During the six months ended June 30, 2026, the Company granted 65,653 stock options at a weighted average exercise price of $254.78 per share based on the grant-date fair value of our stock to employees under the 2016 Plan. The weighted average grant date fair value of options granted was $107.29 per share as determined by the Black-Scholes option valuation model using the following weighted average assumptions: a risk-free interest rate of 3.7%; expected life of 6.8 years based on prior experience; stock volatility of 35.5% based on historical data; and a dividend yield of 0.4%. Stock option expense is recognized over the vesting period, net of forfeitures. During the six months ended June 30, 2026, the Company granted 58,605 stock-settled performance share unit (“PSU”) awards at a weighted average grant-date fair value of $254.79 per share to eligible employees. These awards are earned based on the Company’s performance against pre-established targets, including annual growth rate of revenue and return on invested capital, over a specified performance period. Depending on the achievement of the targets, recipients of stock-settled PSU awards are entitled to receive a certain number of shares of common stock. Shares earned under PSU awards may vary from 0% to 200% of an employee’s targeted award. The fair value of stock-settled PSU awards is based on the market price of our stock at the grant date and is recognized as expense over the performance period, adjusted for estimated target outcomes and net of forfeitures. During the six months ended June 30, 2026, the Company granted 38,299 stock-settled restricted share unit (“RSU”) awards at a weighted average grant-date fair value of $255.47 per share to eligible employees. These awards are earned over a specified performance period. The fair value of stock-settled RSU awards is based on the market price of our stock at the grant date and is recognized as expense over the vesting period, net of forfeitures. Stock-based compensation expense was $10.9 million and $17.5 million for the three and six months ended June 30, 2026. For the three and six months ended June 30, 2025, stock-based compensation expense was $7.4 million and $8.7 million, respectively.

The West Pharmaceutical Services, Inc. 2016 Omnibus Incentive Compensation Plan (the “2016 Plan”) provides for the granting of stock options, stock appreciation rights ("SARs"), restricted stock awards and performance awards to employees and non-employee directors. A committee of the Board of Directors determines the terms and conditions of awards to be granted. Vesting requirements vary by award. In March 2025, the Board of Directors approved, and our stockholders subsequently approved in May 2025, an amendment to the 2016 Plan ("the Amended and Restated 2016 Plan"), which, among other things, added 2.0 million shares of common stock to the maximum number of shares of common stock as to which awards may be granted. Following the approval of the Amended and Restated 2016 Plan, all stock options or SARs that are not forfeited or cancelled will reduce the number of shares available for issuance under the Amended and Restated 2016 Plan by one share for each share subject to the award. Awards issued following the amendment that are payable in common stock (other than stock options or SARs) will reduce the total number of shares available for grant under the Amended and Restated 2016 Plan by an amount equal to 2.0 times the number of shares subject to the award. The reduction was previously equal to 2.5 times the number of shares subject to the award under the 2016 Plan. At June 30, 2026, there were approximately 2.8 million shares remaining in the Amended and Restated 2016 Plan for future grants.

During the six months ended June 30, 2026, the Company granted 65,653 stock options at a weighted average exercise price of $254.78 per share based on the grant-date fair value of our stock to employees under the 2016 Plan. The weighted average grant date fair value of options granted was $107.29 per share as determined by the Black-Scholes option valuation model using the following weighted average assumptions: a risk-free interest rate of 3.7%; expected life of 6.8 years based on prior experience; stock volatility of 35.5% based on historical data; and a dividend yield of 0.4%. Stock option expense is recognized over the vesting period, net of forfeitures.

During the six months ended June 30, 2026, the Company granted 58,605 stock-settled performance share unit (“PSU”) awards at a weighted average grant-date fair value of $254.79 per share to eligible employees. These awards are earned based on the Company’s performance against pre-established targets, including annual growth rate of revenue and return on invested capital, over a specified performance period. Depending on the achievement of the targets, recipients of stock-settled PSU awards are entitled to receive a certain number of shares of common stock. Shares earned under PSU awards may vary from 0% to 200% of an employee’s targeted award. The fair value of stock-settled PSU awards is based on the market price of our stock at the grant date and is recognized as expense over the performance period, adjusted for estimated target outcomes and net of forfeitures.

During the six months ended June 30, 2026, the Company granted 38,299 stock-settled restricted share unit (“RSU”) awards at a weighted average grant-date fair value of $255.47 per share to eligible employees. These awards are earned over a specified performance period. The fair value of stock-settled RSU awards is based on the market price of our stock at the grant date and is recognized as expense over the vesting period, net of forfeitures.