Employee Benefit Plans	12 Months Ended
Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Employee Benefit Plans	NOTE 20 - EMPLOYEE BENEFIT PLANS Retirement Savings Plan Effective June 30, 1999, the Company established the ICF Consulting Group Retirement Savings Plan (the “Retirement Savings Plan”). The Retirement Savings Plan is a defined contribution profit sharing plan with a cash or deferred arrangement under Section 401(k) of the Internal Revenue Code. Participants in the Retirement Savings Plan are able to elect to defer up to 70% of their compensation, subject to statutory limitations, and are entitled to receive 100% employer matching contributions for the first 3% and 50% for the next 2% of their compensation. Contribution expense related to the Retirement Savings Plan for the years ended December 31, 2018, 2017, and 2016, was approximately $16.2 million, $15.1 million, and $14.9 million, respectively. Deferred Compensation Plan Certain key employees of the Company are eligible to defer a specified percentage of their cash compensation by having it contributed to a nonqualified deferred compensation plan. Eligible employees may elect to defer up to 80% of their base salary and up to 100% of performance bonuses, reduced by any amounts withheld for the payment of taxes or other deductions required by law. Participants are at all times 100% vested in their account balances. The Company funds its deferred compensation liabilities by making cash contributions to a Rabbi Trust at the time the salary or bonus being deferred would otherwise be payable to the employee. The liability to plan participants is materially funded at all times and the plan does not have a material net impact on the Company’s results of operations. Employee Stock Purchase Plan The Company has a 2006 Employee Stock Purchase Plan (“ESPP”) under which one million shares have been authorized for issuance. The ESPP allows eligible employees to purchase shares of our common stock through payroll deductions up to $25,000 per calendar year over six-month offering periods at a discount not to exceed 5% of the market value on the date of each purchase period. For the year ended December 31, 2018, 22,320 shares were purchased by employees, at an average purchase price of $63.92, and 702,506 shares remain available for future issuance. The Company does not recognize compensation expense related to the ESPP.

Employee Benefit Plans

12 Months Ended

Dec. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

NOTE 20 - EMPLOYEE BENEFIT PLANS

Retirement Savings Plan

Effective June 30, 1999, the Company established the ICF Consulting Group Retirement Savings Plan (the “Retirement Savings Plan”). The Retirement Savings Plan is a defined contribution profit sharing plan with a cash or deferred arrangement under Section 401(k) of the Internal Revenue Code. Participants in the Retirement Savings Plan are able to elect to defer up to 70% of their compensation, subject to statutory limitations, and are entitled to receive 100% employer matching contributions for the first 3% and 50% for the next 2% of their compensation. Contribution expense related to the Retirement Savings Plan for the years ended December 31, 2018, 2017, and 2016, was approximately $16.2 million, $15.1 million, and $14.9 million, respectively.

Deferred Compensation Plan

Certain key employees of the Company are eligible to defer a specified percentage of their cash compensation by having it contributed to a nonqualified deferred compensation plan. Eligible employees may elect to defer up to 80% of their base salary and up to 100% of performance bonuses, reduced by any amounts withheld for the payment of taxes or other deductions required by law. Participants are at all times 100% vested in their account balances. The Company funds its deferred compensation liabilities by making cash contributions to a Rabbi Trust at the time the salary or bonus being deferred would otherwise be payable to the employee. The liability to plan participants is materially funded at all times and the plan does not have a material net impact on the Company’s results of operations.

Employee Stock Purchase Plan

The Company has a 2006 Employee Stock Purchase Plan (“ESPP”) under which one million shares have been authorized for issuance. The ESPP allows eligible employees to purchase shares of our common stock through payroll deductions up to $25,000 per calendar year over six-month offering periods at a discount not to exceed 5% of the market value on the date of each purchase period. For the year ended December 31, 2018, 22,320 shares were purchased by employees, at an average purchase price of $63.92, and 702,506 shares remain available for future issuance. The Company does not recognize compensation expense related to the ESPP.