Stock-Based Compensation	6 Months Ended
Jun. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [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, 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. At June 30, 2018, there were 3,748,019 shares remaining in the 2016 Plan for future grants. During the six months ended June 30, 2018, we granted 477,501 stock options at a weighted average exercise price of $90.10 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 $20.06 per share as determined by the Black-Scholes option valuation model using the following weighted average assumptions: a risk-free interest rate of 2.7%; expected life of 5.6 years based on prior experience; stock volatility of 19.8% based on historical data; and a dividend yield of 0.7%. Stock option expense is recognized over the vesting period, net of forfeitures. During the six months ended June 30, 2018, we granted 98,065 stock-settled performance share unit (“PSU”) awards at a weighted average grant-date fair value of $89.90 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, 2018, we granted 14,745 stock-settled restricted share unit (“RSU”) awards at a weighted average grant-date fair value of $96.12 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 performance period, net of forfeitures. Total stock-based compensation expense was $6.0 million and $9.4 million for the three and six months ended June 30, 2018, respectively. For the three and six months ended June 30, 2017, stock-based compensation expense was $5.5 million and $9.0 million, respectively.

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, 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. At June 30, 2018, there were 3,748,019 shares remaining in the 2016 Plan for future grants.

During the six months ended June 30, 2018, we granted 477,501 stock options at a weighted average exercise price of $90.10 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 $20.06 per share as determined by the Black-Scholes option valuation model using the following weighted average assumptions: a risk-free interest rate of 2.7%; expected life of 5.6 years based on prior experience; stock volatility of 19.8% based on historical data; and a dividend yield of 0.7%. Stock option expense is recognized over the vesting period, net of forfeitures.

During the six months ended June 30, 2018, we granted 98,065 stock-settled performance share unit (“PSU”) awards at a weighted average grant-date fair value of $89.90 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, 2018, we granted 14,745 stock-settled restricted share unit (“RSU”) awards at a weighted average grant-date fair value of $96.12 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 performance period, net of forfeitures.

Total stock-based compensation expense was $6.0 million and $9.4 million for the three and six months ended June 30, 2018, respectively. For the three and six months ended June 30, 2017, stock-based compensation expense was $5.5 million and $9.0 million, respectively.