Employee Benefit Plans	12 Months Ended
Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefit Plans	12. Employee Benefit Plans ACI 401(k) Plan The ACI 401(k) Plan is a defined contribution plan covering all domestic employees of the Company. Participants may contribute up to 75% of their annual eligible compensation up to a maximum of $18,000 (for employees who are under the age of 50 on December 31, 2017) or a maximum of $24,000 (for employees aged 50 or older on December 31, 2017). After one year of service, the Company matches participant contributions 100% on every dollar deferred to a maximum of 4% of eligible compensation contributed to the plan, not to exceed $4,000 per employee annually. Company contributions charged to expense during the years ended December 31, 2017, 2016, and 2015 was $5.3 million, $5.5 million, and $6.1 million, respectively. ACI Worldwide EMEA Group Personal Pension Scheme The ACI Worldwide EMEA Group Personal Pension Scheme is a defined contribution plan covering substantially all ACI Worldwide (EMEA) Limited (“ACI-EMEA”) employees. For those ACI-EMEA employees who elect to participate in the plan, the Company contributes a minimum of 8.5% of eligible compensation to the plan for employees employed at December 1, 2000 (up to a maximum of 15.5% for employees aged over 55 years on December 1, 2000) or from 6% to 10% of eligible compensation for employees employed subsequent to December 1, 2000. ACI-EMEA contributions charged to expense during the year-ended December 31, 2017, 2016, and 2015 was $1.6 million, $1.7 million, and $1.8 million, respectively.

12. Employee Benefit Plans

ACI 401(k) Plan

The ACI 401(k) Plan is a defined contribution plan covering all domestic employees of the Company. Participants may contribute up to 75% of their annual eligible compensation up to a maximum of $18,000 (for employees who are under the age of 50 on December 31, 2017) or a maximum of $24,000 (for employees aged 50 or older on December 31, 2017). After one year of service, the Company matches participant contributions 100% on every dollar deferred to a maximum of 4% of eligible compensation contributed to the plan, not to exceed $4,000 per employee annually. Company contributions charged to expense during the years ended December 31, 2017, 2016, and 2015 was $5.3 million, $5.5 million, and $6.1 million, respectively.

ACI Worldwide EMEA Group Personal Pension Scheme

The ACI Worldwide EMEA Group Personal Pension Scheme is a defined contribution plan covering substantially all ACI Worldwide (EMEA) Limited (“ACI-EMEA”) employees. For those ACI-EMEA employees who elect to participate in the plan, the Company contributes a minimum of 8.5% of eligible compensation to the plan for employees employed at December 1, 2000 (up to a maximum of 15.5% for employees aged over 55 years on December 1, 2000) or from 6% to 10% of eligible compensation for employees employed subsequent to December 1, 2000. ACI-EMEA contributions charged to expense during the year-ended December 31, 2017, 2016, and 2015 was $1.6 million, $1.7 million, and $1.8 million, respectively.