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Employee Benefit Plans - Narrative (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 USD ($) employee | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Defined Contribution Plan Disclosure [Line Items] |  |  |
Document Fiscal Year Focus | 2018 |  |
Employer matching contributions | $ | $ 2.7 | $ 2.3 | $ 1.8
Number of employees | 1,935 |  |
Entity number of employees, field personnel | 1,678 |  |
Contributions | $ | $ 1.3 | $ 1.5 | $ 1.2
Red Zone |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Multiemployer plan, collective-bargaining arrangement, percentage of contributions required for multiple collective-bargaining arrangements | 65.00% |  |
Orange Zone |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Multiemployer plan, collective-bargaining arrangement, percentage of contributions required for multiple collective-bargaining arrangements | 80.00% |  |
Yellow Zone |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Multiemployer plan, collective-bargaining arrangement, percentage of contributions required for multiple collective-bargaining arrangements | 80.00% |  |
Yellow Zone | Minimum |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Multiemployer plan, collective-bargaining arrangement, percentage of contributions required for multiple collective-bargaining arrangements | 80.00% |  |
Union Members | Nevada, Arizona, California, and Hawaii |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Number of employees | 311 |  |
Number of employees, percent | 19.00% |  |

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