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Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Percentage of customer revenue | 43.00% | 45.00% | 41.00%
Accounts receivable recorded investment past due days | 90 |  |
Self insurance retention liability | $ 2.0 | $ 2.0 | $ 2.0
Self insurance retention Workers' compensation | 1.0 |  |
Letters of credit outstanding, amount | 25.8 |  |
Reclassification of Deferred Tax Asset [Member] |  |  |
Prior period reclassification adjustment | 28.0 |  |
State of Nebraska [Member] |  |  |
Workers' compensation insurance bonds | 27.3 |  |
Workers' Compensation Insurance Carrier [Member] |  |  |
Workers' compensation insurance bonds | $ 6.9 |  |

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