401(k) Retirement Savings Plan, Deferred Compensation Plan and Change in Control Severance Plan	12 Months Ended
Dec. 31, 2011
Compensation And Retirement Disclosure [Abstract]
401(k) Retirement Savings Plan, Deferred Compensation Plan and Change in Control Severance Plan	6. 401(k) Retirement Savings Plan, Deferred Compensation Plan and Change in Control Severance Plan. Under the Company's 401(k) Retirement Savings Plan, which covers eligible employees of On Assignment and its wholly-owned subsidiaries, Assignment Ready Inc., On Assignment Staffing Services, Inc., VISTA, and Oxford, eligible employees may elect to have a portion of their salary deferred and contributed to the plans. The amount of salary deferred, up to certain limits set by the IRS, is not subject to federal and state income tax at the time of deferral, but together with any earnings on deferred amounts, is subject to taxation upon distribution. The plan covers all eligible employees and permits matching or other discretionary contributions at the Company's discretion. Eligible employees may enroll once they complete three months of service prior to the next quarterly offering. The Company pledged to make contributions to the 401(k) plan of $1.1 million in 2011 and made contributions of $0.4 million and $0 in 2010 and 2009, respectively. Effective January 1, 1998, the Company implemented the On Assignment, Inc. Deferred Compensation Plan. The plan permits a select group of management and highly compensated employees and directors that contribute materially to the continued growth, development and future business success of the Company to annually elect to defer up to 100 percent of their base salary, annual bonus, stock option gain or fees on a pre-tax basis and earn tax-deferred returns on these amounts. On September 4, 2008, effective as of January 1, 2008, the Company amended the On Assignment Deferred Compensation Plan so that it applies to deferrals made before January 1, 2005 only (hereinafter referred to as the 1998 Deferred Compensation Plan) and, also effective January 1, 2008, adopted a new plan, called the On Assignment Deferred Compensation Plan - Effective January 1, 2008, applicable to deferrals made on or after January 1, 2005 (referred to herein as the 2008 Deferred Compensation Plan). On April 20, 2011, the Company's Board of Directors authorized and directed the termination of the 1998 Deferred Compensation Plan and the 2008 Deferred Compensation Plan (collectively referred to as the Plans), effective May 2, 2011. Pursuant to the terms of the Plans, the Company may terminate at any time and immediately distribute the accrued account balances held in the Plans in accordance with the provisions of the Plans and applicable law including, but not limited to, Section 409A of the Internal Revenue Code. The Board of Directors believes termination of the Plans is in the best interest of the Company due to low participation and the cost of maintaining the Plans. The Company does not incur any costs or penalties in connection with termination of the Plans. The plans were not intended to be "qualified" within the meaning of IRS Code Section 401(a), rather, the plans were "unfunded and maintained by an employer primarily for the purpose of providing deferred compensation for a select group of management or highly compensated employees" within the meaning of the Employee Retirement Income Security Act of 1974, as amended (ERISA), Sections 201(2), 301(a)(3) and 401(a)(1). Distributions from the 1998 Deferred Compensation Plan are commenced within 60 days after the participant's retirement, death or termination of employment, in a lump sum, or over five, ten or fifteen years, except that payments made upon termination (other than due to death or retirement), are paid in a lump sum if the participant's account balance at the time of termination is less than $25,000. Furthermore, if the Company determines in good faith prior to a change in control that there is a reasonable likelihood that any compensation paid to a participant for a taxable year of the Company would not be deductible by the Company solely by reason of the limitation under IRS Code Section 162(m), (Section 162(m)) then the Company may defer all or any portion of a distribution until the earliest possible date, as determined by the Company in good faith, on which the deductibility of compensation paid or payable to the participant for the taxable year of the Company during which the distribution is made will not be limited by Section 162(m), or if earlier, the effective date of a change in control. Distributions from the 2008 Deferred Compensation Plan are commenced within 60 days following the participant's termination of employment, in a lump sum or in annual installments of up to fifteen years, except that if the participant's account balance is less than the applicable dollar amount specified in IRS Code Section 402(g)(1)(B), in effect for the year in which the distribution is to occur, payment shall be made in a lump sum. Notwithstanding the foregoing, in compliance with certain requirements of IRS Code Section 409A, plan distributions to "specified employees" will commence the first day after the end of the six month period immediately following the date on which the participant experiences a termination of employment. Furthermore, if the Company reasonably anticipates that the Company's deduction with respect to any distribution from the 2008 Deferred Compensation Plan would be limited or eliminated by application of Section 162(m), then to the extent permitted by applicable treasury regulations, payment shall be delayed until the earliest date the Company reasonably anticipates that the deduction of the payment will not be limited or eliminated by application of Section 162(m). The deferred compensation liability under the deferred compensation plans was approximately $1.9 million and $2.2 million at December 31, 2011 and 2010, respectively. Life insurance policies are maintained as a funding source to the plans, under which the Company is the sole owner and beneficiary of such insurance. At December 31, 2011, the cash surrender value of these life insurance policies was $2.1 million, reflected in other current assets in the accompanying Consolidated Balance Sheets. At December 31, 2010, the cash surrender value of these life insurance policies was $2.3 million, reflected in other long-term assets in the accompanying Consolidated Balance Sheets. The Company intends to terminate the life insurance policies in 2012. The Company adopted the On Assignment, Inc. Change in Control Severance Plan (the CIC Plan) to provide severance benefits for officers and certain other employees who are terminated following an acquisition of the Company. This CIC Plan was adopted on February 12, 1998 and amended on August 8, 2004, January 23, 2007, May 21, 2009, December 10, 2009 and May 20, 2010. Under the CIC Plan, if an eligible employee is involuntarily terminated within eighteen months after a change in control, as defined in the CIC Plan, then the employee will be entitled to (i) a payment equal to the employee's annual salary plus the employee's target bonus, payable in a lump sum, and (ii) a lump sum payment representing the cost of continuation of health and welfare benefits, under the Consolidated Omnibus Budget Reconciliation Act of 1985 (COBRA) for periods of time ranging from nine months to eighteen months, for employees with titles of vice president or higher. Severance benefits under the plan range from one month to eighteen months of salary and target bonus, depending on the employee's length of service and position with the Company. The Company entered into an Amended and Restated Executive Change of Control Agreements with the Chief Executive Officer and the Chief Financial Officer on December 11, 2008, primarily for the purpose of causing their existing agreements to meet the requirements of Code Section 409A. These agreements supersede the CIC Plan with respect to these officers and provide, in the event of an involuntary termination occurring within six months and ten days following a change of control of the Company, for the following benefits (i) a lump-sum payment equal to three times (for the Chief Executive Officer's salary plus target bonus) or two and a half times (for the Chief Financial Officer) the sum of the officer's base salary plus target bonus, (ii) eighteen months continuation of the officer's health and welfare benefits and car allowance, (subject to limitations in connection with subsequent employment), (iii) cash payments equal to insurance premiums and retirement and deferred compensation contributions that the Company would have paid (in each case, if any), over a period of eighteen months following termination, and (iv) payment of up to $15,000 of the cost of outplacement services. Additionally, under the arrangements, immediately prior to a change of control, all outstanding Company stock options, restricted stock and stock units held by the officer will become fully vested (and, in the case of options, remain exercisable for an extended period), subject, in the case of certain performance-vesting awards, to any express limitations contained in the officer's employment or other governing agreement. In addition, the agreements entitle the executives to tax gross-up payments in the event that any payments to the executives are subject to "golden parachute" excise taxes under IRS Code Section 280G.

Under the Company's 401(k) Retirement Savings Plan, which covers eligible employees of On Assignment and its wholly-owned subsidiaries, Assignment Ready Inc., On Assignment Staffing Services, Inc., VISTA, and Oxford, eligible employees may elect to have a portion of their salary deferred and contributed to the plans. The amount of salary deferred, up to certain limits set by the IRS, is not subject to federal and state income tax at the time of deferral, but together with any earnings on deferred amounts, is subject to taxation upon distribution. The plan covers all eligible employees and permits matching or other discretionary contributions at the Company's discretion. Eligible employees may enroll once they complete three months of service prior to the next quarterly offering. The Company pledged to make contributions to the 401(k) plan of $1.1 million in 2011 and made contributions of $0.4 million and $0 in 2010 and 2009, respectively.

Effective January 1, 1998, the Company implemented the On Assignment, Inc. Deferred Compensation Plan. The plan permits a select group of management and highly compensated employees and directors that contribute materially to the continued growth, development and future business success of the Company to annually elect to defer up to 100 percent of their base salary, annual bonus, stock option gain or fees on a pre-tax basis and earn tax-deferred returns on these amounts. On September 4, 2008, effective as of January 1, 2008, the Company amended the On Assignment Deferred Compensation Plan so that it applies to deferrals made before January 1, 2005 only (hereinafter referred to as the 1998 Deferred Compensation Plan) and, also effective January 1, 2008, adopted a new plan, called the On Assignment Deferred Compensation Plan - Effective January 1, 2008, applicable to deferrals made on or after January 1, 2005 (referred to herein as the 2008 Deferred Compensation Plan). On April 20, 2011, the Company's Board of Directors authorized and directed the termination of the 1998 Deferred Compensation Plan and the 2008 Deferred Compensation Plan (collectively referred to as the Plans), effective May 2, 2011. Pursuant to the terms of the Plans, the Company may terminate at any time and immediately distribute the accrued account balances held in the Plans in accordance with the provisions of the Plans and applicable law including, but not limited to, Section 409A of the Internal Revenue Code. The Board of Directors believes termination of the Plans is in the best interest of the Company due to low participation and the cost of maintaining the Plans. The Company does not incur any costs or penalties in connection with termination of the Plans. The plans were not intended to be "qualified" within the meaning of IRS Code Section 401(a), rather, the plans were "unfunded and maintained by an employer primarily for the purpose of providing deferred compensation for a select group of management or highly compensated employees" within the meaning of the Employee Retirement Income Security Act of 1974, as amended (ERISA), Sections 201(2), 301(a)(3) and 401(a)(1).

Distributions from the 1998 Deferred Compensation Plan are commenced within 60 days after the participant's retirement, death or termination of employment, in a lump sum, or over five, ten or fifteen years, except that payments made upon termination (other than due to death or retirement), are paid in a lump sum if the participant's account balance at the time of termination is less than $25,000. Furthermore, if the Company determines in good faith prior to a change in control that there is a reasonable likelihood that any compensation paid to a participant for a taxable year of the Company would not be deductible by the Company solely by reason of the limitation under IRS Code Section 162(m), (Section 162(m)) then the Company may defer all or any portion of a distribution until the earliest possible date, as determined by the Company in good faith, on which the deductibility of compensation paid or payable to the participant for the taxable year of the Company during which the distribution is made will not be limited by Section 162(m), or if earlier, the effective date of a change in control.

Distributions from the 2008 Deferred Compensation Plan are commenced within 60 days following the participant's termination of employment, in a lump sum or in annual installments of up to fifteen years, except that if the participant's account balance is less than the applicable dollar amount specified in IRS Code Section 402(g)(1)(B), in effect for the year in which the distribution is to occur, payment shall be made in a lump sum. Notwithstanding the foregoing, in compliance with certain requirements of IRS Code Section 409A, plan distributions to "specified employees" will commence the first day after the end of the six month period immediately following the date on which the participant experiences a termination of employment. Furthermore, if the Company reasonably anticipates that the Company's deduction with respect to any distribution from the 2008 Deferred Compensation Plan would be limited or eliminated by application of Section 162(m), then to the extent permitted by applicable treasury regulations, payment shall be delayed until the earliest date the Company reasonably anticipates that the deduction of the payment will not be limited or eliminated by application of Section 162(m).

The deferred compensation liability under the deferred compensation plans was approximately $1.9 million and $2.2 million at December 31, 2011 and 2010, respectively. Life insurance policies are maintained as a funding source to the plans, under which the Company is the sole owner and beneficiary of such insurance. At December 31, 2011, the cash surrender value of these life insurance policies was $2.1 million, reflected in other current assets in the accompanying Consolidated Balance Sheets. At December 31, 2010, the cash surrender value of these life insurance policies was $2.3 million, reflected in other long-term assets in the accompanying Consolidated Balance Sheets. The Company intends to terminate the life insurance policies in 2012.

The Company adopted the On Assignment, Inc. Change in Control Severance Plan (the CIC Plan) to provide severance benefits for officers and certain other employees who are terminated following an acquisition of the Company. This CIC Plan was adopted on February 12, 1998 and amended on August 8, 2004, January 23, 2007, May 21, 2009, December 10, 2009 and May 20, 2010. Under the CIC Plan, if an eligible employee is involuntarily terminated within eighteen months after a change in control, as defined in the CIC Plan, then the employee will be entitled to (i) a payment equal to the employee's annual salary plus the employee's target bonus, payable in a lump sum, and (ii) a lump sum payment representing the cost of continuation of health and welfare benefits, under the Consolidated Omnibus Budget Reconciliation Act of 1985 (COBRA) for periods of time ranging from nine months to eighteen months, for employees with titles of vice president or higher. Severance benefits under the plan range from one month to eighteen months of salary and target bonus, depending on the employee's length of service and position with the Company.

The Company entered into an Amended and Restated Executive Change of Control Agreements with the Chief Executive Officer and the Chief Financial Officer on December 11, 2008, primarily for the purpose of causing their existing agreements to meet the requirements of Code Section 409A. These agreements supersede the CIC Plan with respect to these officers and provide, in the event of an involuntary termination occurring within six months and ten days following a change of control of the Company, for the following benefits (i) a lump-sum payment equal to three times (for the Chief Executive Officer's salary plus target bonus) or two and a half times (for the Chief Financial Officer) the sum of the officer's base salary plus target bonus, (ii) eighteen months continuation of the officer's health and welfare benefits and car allowance, (subject to limitations in connection with subsequent employment), (iii) cash payments equal to insurance premiums and retirement and deferred compensation contributions that the Company would have paid (in each case, if any), over a period of eighteen months following termination, and (iv) payment of up to $15,000 of the cost of outplacement services. Additionally, under the arrangements, immediately prior to a change of control, all outstanding Company stock options, restricted stock and stock units held by the officer will become fully vested (and, in the case of options, remain exercisable for an extended period), subject, in the case of certain performance-vesting awards, to any express limitations contained in the officer's employment or other governing agreement. In addition, the agreements entitle the executives to tax gross-up payments in the event that any payments to the executives are subject to "golden parachute" excise taxes under IRS Code Section 280G.