Employee Benefit Plans - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accrued matching contribution	$ 1,500,000	$ 1,400,000
Kforce common stock held by both plans (in shares)	201	218
Percentage of discount on shares purchased under employee stock purchase plan	5.00%
Employee stock purchase plan (in shares)	34	26	35
Average purchase price (in dollars per share)	$ 19.37	$ 22.61	$ 19.76
Life Insurance, Corporate or Bank Owned, Amount	$ 213,100,000
Gains (losses) attributable to the investments in bond mutual funds	0	$ 0	$ 0
Rabbi Trust
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Deferred Compensation Plan Assets	27,300,000	25,500,000
Supplemental Executive Retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Payment to Participants under the SERP	$ 0
Normal retirement age	65 years
Early retirement age	55 years
Vesting percentage under plan for attaining age 55 and 10 years	100.00%
Defined benefit plan arrangement minimum age	55 years
Completed at least credited service period	10 years
Vesting percentage under plan prior to attaining age 55 and 10 years	0.00%
Defined benefit plan employees minimum requisition period under specific conditions	5 years
Benefits payable targeted percentage	45.00%
Period in which the executive officer earned the highest salary and bonus	3 years
Employment period for computation of benefit	10 years
Eligible age under condition one for reduced benefits under the plan	62 years
Eligible service under condition one for reduced benefits under plan	10 years
Eligible age under condition two for reduced benefits under plan	55 years
Eligible service under condition two for reduced benefits under plan	25 years
Lump sum payment period	10 years
Payments made under the SERHP		0
Accumulated benefit obligation	$ 12,700,000	11,000,000
Employer contributions to benefit plans	0
Expected future benefit payments, next 12 months	0
Supplemental Executive Retirement Health Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Payments made under the SERHP			3,900,000
Settlement gain (loss)			(725,000)
Non-Qualified Deferred Compensation Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current deferred compensation liability	2,700,000	2,300,000
Deferred compensation plan	27,500,000	24,200,000
Compensation expenses (income)	$ 881,000	$ 401,000	$ (187,000)