Annual report pursuant to Section 13 and 15(d)

Geographic Information (Details)

v3.8.0.1
Geographic Information (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]                      
Long-lived assets $ 361,746       $ 324,776       $ 361,746 $ 324,776  
Revenues 211,133 $ 204,744 $ 166,665 $ 134,610 174,225 $ 180,598 $ 162,628 $ 133,776 717,152 651,227 $ 630,832
United States                      
Revenues from External Customers and Long-Lived Assets [Line Items]                      
Long-lived assets 343,344       306,908       343,344 306,908  
Revenues                 665,793 588,791 567,815
Canada                      
Revenues from External Customers and Long-Lived Assets [Line Items]                      
Long-lived assets 17,082       16,454       17,082 16,454  
Revenues                 42,186 49,706 48,968
Other                      
Revenues from External Customers and Long-Lived Assets [Line Items]                      
Long-lived assets $ 1,320       $ 1,414       1,320 1,414  
Revenues                 $ 9,173 $ 12,730 $ 14,049