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Accounting Policies (Details) | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Oct. 01, 2019 USD ($) | Dec. 31, 2018 USD ($) | Oct. 01, 2010 USD ($) | Sep. 30, 2010 USD ($)
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] |  |  |  |  |  |  |  |
Percentage of eligible compensation matched, maximum |  | 3.00% |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |  |
Revenues(1) | [1] | $ 4,973,070,000 | $ 4,287,004,000 | $ 4,314,804,000 |  |  |  |
Goodwill and Intangible Assets Disclosure [Abstract] |  |  |  |  |  |  |  |
Goodwill, Impairment Loss |  | 0 | 0 | 0 |  |  |  |
Goodwill, Gross |  | 21,200,000 |  |  |  |  |  |
Goodwill, Impaired, Accumulated Impairment Loss |  | 8,500,000 |  |  |  |  |  |
Goodwill |  | $ 12,700,000 |  |  |  |  |  |
Health Insurance Costs [Abstract] |  |  |  |  |  |  |  |
Percentage of our health insurance coverage provided by United |  | 87.00% |  |  |  |  |  |
Number of days in advance of the beginning of a reporting quarter carrier establishes cash funding rates |  | 90 days |  |  |  |  |  |
Prepaid health insurance |  | $ 9,000,000 | 9,000,000 |  |  |  |  |
Required deposit for health care costs |  | 6,500,000 |  |  |  |  |  |
Portion of insurance costs that is less than the agreed upon surplus included in accrued health insurance costs a cnt liab |  | (31,000,000) |  |  |  |  |  |
Prepaid health insurance current and noncurrent |  | (22,000,000) |  |  |  |  |  |
Premiums owed to United |  | 12,600,000 |  |  |  |  |  |
Benefits Costs Incurred Related to Run-off |  | (4,900,000) | (200,000) | (2,300,000) |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Property, Plant and Equipment, Gross |  | 512,995,000 | 495,078,000 |  |  |  |  |
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment |  | 302,272,000 | 278,822,000 |  |  |  |  |
Property and equipment, net |  | 210,723,000 | 216,256,000 |  |  |  |  |
Amortization of capitalized computer software costs |  | 10,900,000 | 8,700,000 | 7,800,000 |  |  |  |
Unamortized computer software costs |  | $ 35,400,000 | 32,600,000 |  |  |  |  |
Segment Reporting [Abstract] |  |  |  |  |  |  |  |
Number of reportable segments (integer) |  | 1 |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Additional General Disclosures [Abstract] |  |  |  |  |  |  |  |
Number of stock-based employee compensation plans |  | 1 |  |  |  |  |  |
Stock awards vesting period |  | 3 years |  |  |  |  |  |
Percentage of grants issued to directors that are vested for annual award grants. |  | 100.00% |  |  |  |  |  |
Workers' Compensation Costs [Abstract] |  |  |  |  |  |  |  |
Workers' Compensation, Maximum economic burden first layer of claims per occurrence |  |  |  |  | $ 1,500,000 |  |  | $ 1,000,000
Workers' Compensation, Maximum aggregate economic burden for claims in excess of first layer cap per policy year |  |  |  |  | $ 6,000,000 |  | $ 6,000,000 |
Decrease Increase in accrued workers' compensation costs for changes in estimated losses |  | $ 41,700,000 | 42,100,000 | 31,700,000 |  |  |  |
U.S. Treasury rates that correspond with the weighted average estimated claim payout period |  | 0.60% |  |  |  |  |  |
Restricted Cash and Cash Equivalents, Current |  | $ 46,929,000 | 45,522,000 | 49,295,000 |  | $ 42,227,000 |  |
Deposits workers' compensation |  | 185,027,000 | 186,331,000 | 175,913,000 |  | 166,474,000 |  |
Incurred but not paid workers' compensation liabilities |  |  |  |  |  |  |  |
Liability for Unpaid Claims and Claims Adjustment Expense, Adjustments |  |  | 240,761,000 | 242,904,000 |  |  |  |
Workers' Compensation Expense |  | 48,097,000 | 42,639,000 |  |  |  |  |
Workers' Compensation Discount, Changed during period |  | 898,000 | (740,000) |  |  |  |  |
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid |  | (48,337,000) | (45,522,000) |  |  |  |  |
Ending Balance |  | 239,623,000 | 240,761,000 |  |  |  |  |
Current portion of accrued claims |  | 46,929,000 | 45,522,000 |  |  |  |  |
Long-term portion of accrued claims |  | 192,694,000 | 195,239,000 |  |  |  |  |
Workers' compensation administrative fees accrued |  | 3,600,000 | 2,700,000 |  |  |  |  |
Undiscounted accrued workers' compensation costs |  | $ 255,100,000 | 257,900,000 |  |  |  |  |
Time period incurred claims expected to be paid recorded as restricted cash |  | 1 year |  |  |  |  |  |
Return Of Excess Claim Funds |  | $ 35,100,000 |  |  |  |  |  |
Restricted Cash and Cash Equivalents, Current |  | 46,929,000 | 45,522,000 | 49,295,000 |  | 42,227,000 |  |
Deposits workers' compensation |  | $ 185,027,000 | $ 186,331,000 | $ 175,913,000 |  | $ 166,474,000 |  |
Time period estimate of incurred claim costs to be paid included in short term liabilities |  | 1 year |  |  |  |  |  |
Minimum [Member] |  |  |  |  |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 5 years | 7 years |  |  |  |  |
Corporate Employees [Member] |  |  |  |  |  |  |  |
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] |  |  |  |  |  |  |  |
Percentage the entity matches of eligible corporate employees' contributions |  | 100.00% |  |  |  |  |  |
Percentage of eligible compensation matched, maximum |  | 6.00% | 6.00% | 6.00% |  |  |  |
Matching contributions to the plan |  | $ 8,200,000 | $ 12,600,000 | $ 11,400,000 |  |  |  |
Worksite Employees [Member] |  |  |  |  |  |  |  |
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] |  |  |  |  |  |  |  |
Percentage of eligible compensation matched, Minimum |  | 0.00% |  |  |  |  |  |
Percentage of eligible compensation matched, maximum |  | 6.00% |  |  |  |  |  |
Matching contributions to the plan |  | $ 244,100,000 | 199,200,000 | 198,200,000 |  |  |  |
Land [Member] |  |  |  |  |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Property, Plant and Equipment, Gross |  | 6,215,000 | 6,215,000 |  |  |  |  |
Building and Building Improvements [Member] |  |  |  |  |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Property, Plant and Equipment, Gross |  | $ 206,449,000 | $ 125,704,000 |  |  |  |  |
Building and Building Improvements [Member] | Minimum [Member] |  |  |  |  |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 5 years |  |  |  |  |  |
Building and Building Improvements [Member] | Maximum [Member] |  |  |  |  |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  |  | 30 years |  |  |  |  |
Computer hardware and software [Member] |  |  |  |  |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Property, Plant and Equipment, Gross |  | $ 136,346,000 | $ 129,213,000 |  |  |  |  |
Computer hardware and software [Member] | Minimum [Member] |  |  |  |  |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 2 years |  |  |  |  |  |
Computer hardware and software [Member] | Maximum [Member] |  |  |  |  |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  |  | 5 years |  |  |  |  |
Software Development Costs [Member] |  |  |  |  |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Property, Plant and Equipment, Gross |  | $ 112,433,000 | $ 100,762,000 |  |  |  |  |
Software Development Costs [Member] | Minimum [Member] |  |  |  |  |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  | 3 years |  |  |  |  |  |
Software Development Costs [Member] | Maximum [Member] |  |  |  |  |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Estimated useful lives of property and equipment |  |  | 5 years |  |  |  |  |
Construction in Progress [Member] |  |  |  |  |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Property, Plant and Equipment, Gross |  | $ 0 | $ 84,668,000 |  |  |  |  |
Furniture, Fixtures and Other [Member] |  |  |  |  |  |  |  |
Impaired Long-Lived Assets Held and Used [Line Items] |  |  |  |  |  |  |  |
Property, Plant and Equipment, Gross |  | 51,552,000 | 48,516,000 |  |  |  |  |
Northeast [Member] |  |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |  |
Revenues(1) |  | 1,390,156,000 | 1,189,837,000 | 1,135,771,000 |  |  |  |
Southeast [Member] |  |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |  |
Revenues(1) |  | 630,342,000 | 509,846,000 | 499,201,000 |  |  |  |
Central [Member] |  |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |  |
Revenues(1) |  | 867,914,000 | 761,905,000 | 743,514,000 |  |  |  |
Southwest [Member] |  |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |  |
Revenues(1) |  | 993,747,000 | 935,634,000 | 1,001,845,000 |  |  |  |
West [Member] |  |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |  |
Revenues(1) |  | 1,033,996,000 | 839,347,000 | 880,434,000 |  |  |  |
Other Revenues [Member] |  |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |  |
Revenues(1) |  | $ 56,915,000 | $ 50,435,000 | $ 54,039,000 |  |  |  |
[1] | Revenues are comprised of gross billings less worksite employee (“WSEE”) payroll costs as follows:
| Year ended December 31,
(in thousands) | 2021 | 2020 | 2019
Gross billings | $ | 33,318,693 |  | $ | 28,168,611 |  | $ | 27,212,010 |
Less: WSEE payroll cost | 28,345,623 |  | 23,881,607 |  | 22,897,206 |
Revenues | $ | 4,973,070 |  | $ | 4,287,004 |  | $ | 4,314,804 |

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- Definition The number of days in advance of the beginning of a reporting quarter that United Healthcare establishes cash funding rates. + References No definition available. + Details
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