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Accounting Policies (Details) - USD ($) | 3 Months Ended | 6 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019 | Dec. 31, 2019 | Oct. 01, 2019 | Dec. 31, 2018
Health Insurance Costs [Abstract] |  |  |  |  |  |  |
Percentage of our health insurance coverage provided by United | 87.00% |  | 87.00% |  |  |  |
Number of days in advance of the beginning of a reporting quarter United establishes cash funding rates |  |  | 90 days |  |  |  |
Required accumulated cash surplus | $ 9,000,000.0 |  | $ 9,000,000.0 |  | $ 9,000,000 |  |
Required deposit equal to approximately one day of claims funding activity | 6,500,000 |  | 6,500,000 |  |  |  |
Amount which plan costs were less than the net premiums paid and owed | 19,500,000 |  | 19,500,000 |  |  |  |
Prepaid health insurance, current | 10,500,000 |  | 10,500,000 |  |  |  |
Premiums owed to United | 23,400,000 |  | 23,400,000 |  |  |  |
Benefits costs incurred (reduced) related to run-off | 3,000,000.0 | $ (3,500,000) | 3,000,000.0 | $ (3,500,000) |  |  |
Workers' Compensation Costs [Abstract] |  |  |  |  |  |  |
Company's maximum economic burden for the first layer of claims per occurrence | 1,000,000 |  | 1,000,000 |  |  | $ 1,500,000 |
Company's maximum aggregate economic burden for claims in excess of 1 million per policy year | 6,000,000 |  | 6,000,000 |  |  | $ 6,000,000 |
Decrease Increase in accrued workers' compensation costs for changes in estimated losses |  |  | $ 22,200,000 | $ 19,000,000.0 |  |  |
U.S. Treasury rates that correspond with the weighted average estimated claim payout period (in hundredths) |  |  | 0.80% | 2.30% |  |  |
Incurred but not paid workers compensation liabilities [Abstract] |  |  |  |  |  |  |
Liability for Unpaid Claims and Claims Adjustment Expense, Adjustments |  |  |  |  | 242,904,000 |  | $ 229,639,000
Workers' Compensation Expense |  |  | $ 21,888,000 | $ 27,299,000 |  |  |
Present value discount, net of accretion |  |  | 223,000 | (2,703,000) |  |  |
Paid claims |  |  | (22,298,000) | (22,727,000) |  |  |
WorkersCompensationLiabilityNetOfAdminFeesCurrent | 45,216,000 | 43,267,000 | 45,216,000 | 43,267,000 |  |  |
Long-term portion of accrued claims | 197,501,000 | 188,241,000 | 197,501,000 | 188,241,000 | 193,609,000 |  |
Ending balance | 242,717,000 | 231,508,000 | 242,717,000 | 231,508,000 |  |  |
Workers compensation administrative fees accrued | 3,400,000 |  | 3,400,000 |  |  |  |
Undiscounted accrued workers' compensation costs |  |  | $ 261,400,000 | 250,900,000 |  |  |
Time period incurred claims expected to be paid recorded as restricted cash |  |  | 1 year |  |  |  |
Time period incurred claims expected to be paid, included in deposits, a long-term asset |  |  | Greater than 1 year |  |  |  |
Restricted cash | 45,216,000 | 43,268,000 | $ 45,216,000 | 43,268,000 | 49,295,000 |  | 42,227,000
Deposits workers compensation | 177,944,000 | 187,728,000 | $ 177,944,000 | 187,728,000 | 175,913,000 |  | $ 166,474,000
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 |  |  |  |
ReturnofExcessClaimFunds |  |  | $ 24,800,000 |  |  |  |
Revenue from Contract with Customer [Abstract] |  |  |  |  |  |  |
Unbilled | 463,100,000 |  | 463,100,000 |  | $ 448,100,000 |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |
Revenue from Contract with Customer, Excluding Assessed Tax | 993,366,000 | 1,043,316,000 | 2,222,849,000 | 2,196,326,000 |  |  |
Northeast [Member] |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |
Revenue from Contract with Customer, Excluding Assessed Tax | 273,543,000 | 270,475,000 | 617,401,000 | 581,422,000 |  |  |
Southeast [Member] |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |
Revenue from Contract with Customer, Excluding Assessed Tax | 117,013,000 | 120,148,000 | 258,175,000 | 250,054,000 |  |  |
Central [Member] |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |
Revenue from Contract with Customer, Excluding Assessed Tax | 177,022,000 | 179,443,000 | 388,314,000 | 375,196,000 |  |  |
Southwest [Member] |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |
Revenue from Contract with Customer, Excluding Assessed Tax | 222,734,000 | 244,462,000 | 494,658,000 | 514,294,000 |  |  |
West [Member] |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |
Revenue from Contract with Customer, Excluding Assessed Tax | 192,310,000 | 215,639,000 | 439,121,000 | 448,842,000 |  |  |
Other Revenues [Member] |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |
Revenue from Contract with Customer, Excluding Assessed Tax | $ 10,744,000 | $ 13,149,000 | $ 25,180,000 | $ 26,518,000 |  |  |

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