Annual report pursuant to Section 13 and 15(d)

Goodwill and Intangible Assets - Additional Information (Details)

v3.8.0.1
Goodwill and Intangible Assets - Additional Information (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Goodwill [Line Items]      
Goodwill $ 56,135 $ 57,976 $ 59,085
Minimum      
Goodwill [Line Items]      
Percent of goodwill fair value that exceeds carrying value 20.00% 13.00%  
Intangible assets amortization period 1 year    
Minimum | Customer contracts      
Goodwill [Line Items]      
Intangible assets amortization period 1 year    
Minimum | Customer relationships, noncompete agreements, technology and trade names      
Goodwill [Line Items]      
Intangible assets amortization period 4 years    
Maximum      
Goodwill [Line Items]      
Intangible assets amortization period 15 years    
Maximum | Customer contracts      
Goodwill [Line Items]      
Intangible assets amortization period 5 years    
Maximum | Customer relationships, noncompete agreements, technology and trade names      
Goodwill [Line Items]      
Intangible assets amortization period 15 years    
Canada      
Goodwill [Line Items]      
Goodwill $ 3,494 $ 3,262 3,162
U.S. Regions      
Goodwill [Line Items]      
Goodwill $ 24,759 $ 24,759 $ 24,759
U.S. Regions | Southwest Reporting Unit      
Goodwill [Line Items]      
Percent of goodwill fair value that exceeds carrying value   9.00%  
Goodwill   $ 16,800