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v3.3.1.900

Accounting Policies (Details) $ in Thousands | 3 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 31, 2014 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Oct. 01, 2010 USD ($) | Sep. 30, 2010 USD ($)
Segment Reporting [Abstract] |  |  |  |  |  |  |  |
Number of reportable segments (integer) |  | 1 |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Amortization of capitalized computer software costs |  | $ 3,300 | $ 4,100 | $ 3,600 |  |  |  |
Unamortized computer software costs |  |  |  |  | $ 7,100 | $ 6,000 |  |
Asset impairment charge due to change in office consolidation plans | $ 1,200 |  |  |  |  |  |  |
Health Insurance Costs [Abstract] |  |  |  |  |  |  |  |
Number of days cash in advance of beginning of reporting quarter United establishes cash funding rates |  | 90 days |  |  |  |  |  |
Prepaid health insurance |  |  |  |  | 9,000 | 9,000 |  |
Required deposit for health care costs |  |  |  |  | 3,500 |  |  |
Amount which Plan Costs were less than the net premiums paid and owed |  |  |  |  | 2,200 |  |  |
Portion of insurance costs that is less than the agreed upon surplus included in accrued health insurance costs a cnt liab |  |  |  |  | (6,800) |  |  |
Premiums owed to United |  |  |  |  | 3,100 |  |  |
Workers' Compensation Costs [Abstract] |  |  |  |  |  |  |  |
Company's maximum economic burden for the first layer of claims per occurrence |  |  |  |  |  |  |  | $ 1,000
Company's maximum aggregate economic burden for claims in excess of $1 million per policy year |  |  |  |  |  |  | $ 5,000 |
Reduction in accrued workers' compensation costs for changes in estimated losses |  | $ 1,300 | $ 2,900 |  |  |  |  |
U.S. Treasury rates that correspond with the weighted average estimated claim payout period (in hundredths) |  | 1.00% | 1.00% |  |  |  |  |
Incurred but not paid workers' compensation liabilities |  |  |  |  |  |  |  |
Beginning balance |  | $ 136,088 | $ 120,833 |  |  |  |  |
Accrued claims |  | 67,559 | 55,971 |  |  |  |  |
Present value discount |  | (3,095) | (1,998) |  |  |  |  |
Paid claims |  | (38,368) | (38,718) |  |  |  |  |
Ending balance | 136,088 | 162,184 | 136,088 | 120,833 |  |  |  |
Current portion of accrued claims |  |  |  |  | 37,438 | 44,040 |  |
Long-term portion of accrued claims |  |  |  |  | 124,746 | 92,048 |  |
Ending Balance | $ 136,088 | 136,088 | 120,833 | 120,833 | 162,184 | 136,088 |  |
Current portion of workers' compensation administrative fees accrued |  |  |  |  | 1,600 |  |  |
Undiscounted accrued workers' compensation costs |  | $ 172,300 | 145,800 |  |  |  |  |
Time period incurred claims expected to be paid recorded as restricted cash |  | 1 year |  |  |  |  |  |
Return Of Excess Claim Funds |  | $ 5,300 |  |  |  |  |  |
Time period incurred claims expected to be paid, included in deposits, a long-term asset |  | Greater than 1 year |  |  |  |  |  |
Restricted Cash and Cash Equivalents, Current |  |  |  |  | 37,418 | 44,040 |  |
Deposits - workers' compensation |  |  |  |  | $ 136,462 | $ 113,934 |  |
Time period estimate of incurred claim costs to be paid included in short term liabilities |  | 1 year |  |  |  |  |  |
Time period incurred claims expected to be paid, included in long-term liabilities |  | Greater than 1 year |  |  |  |  |  |
Stock-Based Compensation [Abstract] |  |  |  |  |  |  |  |
Number of stock-based employee compensation plans |  |  |  |  | 2 |  |  |
Vesting period for Initial grants to new members of the Board of Directors |  | 3 years |  |  |  |  |  |
Vesting period for officers and other management to be eligible for restricted stock grants, minimum |  | 3 years |  |  |  |  |  |
Vesting period for officers and other management to be eligible for restricted stock grants, maximum |  | 5 years |  |  |  |  |  |
Percentage of annual grants issued to directors that are vested (in hundredths) |  | 100.00% |  |  |  |  |  |
New Accounting Pronouncements [Abstract] |  |  |  |  |  |  |  |
Prior Period Reclassification Adjustment |  |  | 6,300 |  |  |  |  |
Minimum [Member] |  |  |  |  |  |  |  |
Other Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Other Intangible Assets, useful life |  | 3 years |  |  |  |  |  |
Maximum [Member] |  |  |  |  |  |  |  |
Other Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Other Intangible Assets, useful life |  | 10 years |  |  |  |  |  |
Corporate Employees [Member] |  |  |  |  |  |  |  |
Company-Sponsored 401 (k) Plans [Abstract] |  |  |  |  |  |  |  |
Percentage match of eligible corporate employees' contributions (in hundredths) |  | 50.00% |  |  |  |  |  |
Percentage of eligible compensation matched, minimum (in hundredths) |  | 0.00% |  |  |  |  |  |
Percentage of eligible compensation matched, maximum (in hundredths) |  | 6.00% |  |  |  |  |  |
Worksite Employees [Member] |  |  |  |  |  |  |  |
Company-Sponsored 401 (k) Plans [Abstract] |  |  |  |  |  |  |  |
Percentage of eligible compensation matched, minimum (in hundredths) |  | 0.00% |  |  |  |  |  |
Percentage of eligible compensation matched, maximum (in hundredths) |  | 6.00% |  |  |  |  |  |
Matching contributions to the Plans |  | $ 95,300 | 78,400 | 71,700 |  |  |  |
Corporate Plan and Worksite Employee Plan [Member] |  |  |  |  |  |  |  |
Company-Sponsored 401 (k) Plans [Abstract] |  |  |  |  |  |  |  |
Matching contributions to the Plans |  | $ 98,700 | $ 81,500 | $ 74,700 |  |  |  |
Buildings and Improvements [Member] | Minimum [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 5 years |  |  |  |  |  |
Buildings and Improvements [Member] | Maximum [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 30 years |  |  |  |  |  |
Computer Hardware and Software and Acquired Technologies [Member] | Minimum [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 2 years |  |  |  |  |  |
Computer Hardware and Software and Acquired Technologies [Member] | Maximum [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 5 years |  |  |  |  |  |
Software Development Costs [Member] | Minimum [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 3 years |  |  |  |  |  |
Software Development Costs [Member] | Maximum [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 5 years |  |  |  |  |  |
Furniture, Fixtures and Other [Member] | Minimum [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 5 years |  |  |  |  |  |
Furniture, Fixtures and Other [Member] | Maximum [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 7 years |  |  |  |  |  |
Aircraft [Member] | Minimum [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 15 years |  |  |  |  |  |
Aircraft [Member] | Maximum [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 20 years |  |  |  |  |  |

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