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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%