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Commitments and Contingencies (Details) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 USD ($) property | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Other Commitments [Line Items] |  |  |
Self Insurance Reserve | $ 2,100 | $ 1,800 |
Operating Leases, Rent Expense | 26,400 | 25,600 | $ 21,600
Deferred Rent Credit, Current | 1,200 | 600 |
Deferred Rent Credit, Noncurrent | 5,000 | 5,200 |
Workerscompensationreceivable | 12,702 | 14,001 |
Letters of Credit Outstanding, Amount | 4,400 | 4,000 |
Commitment and contingencies [Line Items] |  |  |
Costs and Expenses, Related Party | 1,300 | $ 1,300 | $ 1,300
Operating Leases |  |  |
2018 | 20,387 |  |
2019 | 17,520 |  |
2020 | 14,698 |  |
2021 | 12,146 |  |
2022 | 8,089 |  |
Thereafter | 7,267 |  |
Total | 80,107 |  |
Related Party |  |  |
2018 | 1,302 |  |
2019 | 1,282 |  |
2020 | 1,314 |  |
2021 | 1,347 |  |
2022 | 1,380 |  |
Thereafter | 2,618 |  |
Total | 9,243 |  |
Purchase Obligation, Due in Next Twelve Months | 10,283 |  |
Purchase Obligation, Due in Second Year | 8,362 |  |
Purchase Obligation, Due in Third Year | 1,055 |  |
Purchase Obligation, Due in Fourth Year | 0 |  |
Purchase Obligation, Due in Fifth Year | 0 |  |
Purchase Obligation, Due after Fifth Year | 0 |  |
Purchase Obligation | 19,700 |  |
Total |  |  |
2018 | 31,972 |  |
2019 | 27,164 |  |
2020 | 17,067 |  |
2021 | 13,493 |  |
2022 | 9,469 |  |
Thereafter | 9,885 |  |
Total | $ 109,050 |  |
Apex Systems |  |  |
Commitment and contingencies [Line Items] |  |  |
Number of Leased Properties Owned by Related Parties | property | 2 |  |

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