Retirement Benefits	12 Months Ended
Dec. 31, 2017
Retirement Benefits [Abstract]
Retirement Benefits	Retirement Benefits U.S. Defined Contribution Plans The Company provides a qualified defined contribution plan covering substantially all U.S.-based full-time employees, except officers and certain other employees. The plan offers a savings feature with Company matching contributions. Assets of this plan are held by an independent trustee for the sole benefit of participating employees. A nonqualified plan is provided for officers and certain other employees. This plan includes provisions for salary deferrals and Company matching contributions. In addition to the plans above, the Company also provides a qualified plan and a nonqualified plan to certain U.S.-based temporary employees. The liability for the nonqualified plans was $188.3 million and $166.7 million as of year-end 2017 and 2016, respectively, and is included in current accrued payroll and related taxes and noncurrent accrued retirement benefits. The cost of participants’ earnings or loss on this liability, which were included in SG&A expenses, were earnings of $22.3 million in 2017, earnings of $10.5 million in 2016 and loss of $1.6 million in 2015. In connection with the administration of these plans, the Company has purchased company-owned variable universal life insurance policies insuring the lives of certain current and former officers and key employees. The cash surrender value of these policies, which is based primarily on investments in mutual funds and can only be used for payment of the Company’s obligations related to the nonqualified deferred compensation plan noted above, was $188.7 million and $165.0 million at year-end 2017 and 2016, respectively. The cash surrender value of these insurance policies is included in other assets. Tax-free earnings on these assets, which were included in SG&A expenses and which offset the related earnings or loss on the liability, were $22.3 million in 2017, $9.7 million in 2016 and $0.3 million in 2015. The net expense for retirement benefits for the qualified and nonqualified plans, including Company matching contributions for full-time employees, totaled $8.6 million in 2017, $9.0 million in 2016 and $5.7 million in 2015. This expense in included in total SG&A expenses in the consolidated statement of earnings. The expense related to retirement plan contributions for temporary employees, which is included in cost of services, is reimbursed by our customers. International Defined Benefit Plans The Company has several defined benefit pension plans in locations outside of the United States. The total projected benefit obligation, assets and unfunded liability for these plans as of year-end 2017 were $13.3 million, $8.4 million and $4.9 million, respectively. The total projected benefit obligation, assets and unfunded liability for these plans as of year-end 2016 were $11.6 million, $7.6 million and $4.0 million, respectively. Total pension expense for these plans was $0.4 million in 2017 and 2016 and $0.3 million in 2015. Pension contributions and the amount of accumulated other comprehensive income expected to be recognized in 2018 are not significant.

Retirement Benefits

U.S. Defined Contribution Plans

The Company provides a qualified defined contribution plan covering substantially all U.S.-based full-time employees, except officers and certain other employees. The plan offers a savings feature with Company matching contributions. Assets of this plan are held by an independent trustee for the sole benefit of participating employees.

A nonqualified plan is provided for officers and certain other employees. This plan includes provisions for salary deferrals and Company matching contributions.

In addition to the plans above, the Company also provides a qualified plan and a nonqualified plan to certain U.S.-based temporary employees.

The liability for the nonqualified plans was $188.3 million and $166.7 million as of year-end 2017 and 2016, respectively, and is included in current accrued payroll and related taxes and noncurrent accrued retirement benefits. The cost of participants’ earnings or loss on this liability, which were included in SG&A expenses, were earnings of $22.3 million in 2017, earnings of $10.5 million in 2016 and loss of $1.6 million in 2015. In connection with the administration of these plans, the Company has purchased company-owned variable universal life insurance policies insuring the lives of certain current and former officers and key employees. The cash surrender value of these policies, which is based primarily on investments in mutual funds and can only be used for payment of the Company’s obligations related to the nonqualified deferred compensation plan noted above, was $188.7 million and $165.0 million at year-end 2017 and 2016, respectively. The cash surrender value of these insurance policies is included in other assets. Tax-free earnings on these assets, which were included in SG&A expenses and which offset the related earnings or loss on the liability, were $22.3 million in 2017, $9.7 million in 2016 and $0.3 million in 2015.

The net expense for retirement benefits for the qualified and nonqualified plans, including Company matching contributions for full-time employees, totaled $8.6 million in 2017, $9.0 million in 2016 and $5.7 million in 2015. This expense in included in total SG&A expenses in the consolidated statement of earnings. The expense related to retirement plan contributions for temporary employees, which is included in cost of services, is reimbursed by our customers.

International Defined Benefit Plans

The Company has several defined benefit pension plans in locations outside of the United States. The total projected benefit obligation, assets and unfunded liability for these plans as of year-end 2017 were $13.3 million, $8.4 million and $4.9 million, respectively. The total projected benefit obligation, assets and unfunded liability for these plans as of year-end 2016 were $11.6 million, $7.6 million and $4.0 million, respectively. Total pension expense for these plans was $0.4 million in 2017 and 2016 and $0.3 million in 2015. Pension contributions and the amount of accumulated other comprehensive income expected to be recognized in 2018 are not significant.