Quarterly report pursuant to Section 13 or 15(d)

Business Segment Information (Details)

v3.8.0.1
Business Segment Information (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Jun. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Segment Reporting Information [Line Items]          
Revenues $ 204,744 $ 180,598   $ 506,019 $ 477,002
Interest income 40 12   86 36
Interest expense 2,448 1,887   6,567 5,121
Depreciation and amortization of intangible assets 6,185 5,802   17,591 16,751
Income (loss) before taxes, excluding unallocated corporate activity 19,511 18,153   38,234 36,530
Canada          
Segment Reporting Information [Line Items]          
Unallocated corporate activity     $ (1,934)    
Operating Segments | U.S. Regions          
Segment Reporting Information [Line Items]          
Revenues 78,185 83,652   180,770 195,856
Interest income 0 0   0 0
Interest expense 0 0   0 0
Depreciation and amortization of intangible assets 105 116   246 390
Income (loss) before taxes, excluding unallocated corporate activity 4,411 7,918   4,242 12,732
Operating Segments | U.S. Federal          
Segment Reporting Information [Line Items]          
Revenues 63,873 46,498   170,903 128,266
Interest income 14 2   29 7
Interest expense 262 278   795 666
Depreciation and amortization of intangible assets 644 686   1,951 1,913
Income (loss) before taxes, excluding unallocated corporate activity 8,753 5,338   23,079 16,303
Operating Segments | Canada          
Segment Reporting Information [Line Items]          
Revenues 14,719 12,018   33,211 40,023
Interest income 0 0   1 0
Interest expense 500 493   1,434 1,243
Depreciation and amortization of intangible assets 303 288   878 788
Income (loss) before taxes, excluding unallocated corporate activity 1,537 (154)   1,638 (1,457)
Operating Segments | Small-Scale Infrastructure          
Segment Reporting Information [Line Items]          
Revenues 27,295 21,790   64,889 61,543
Interest income 26 10   56 29
Interest expense 1,673 1,116   4,300 3,212
Depreciation and amortization of intangible assets 4,636 4,063   13,109 11,663
Income (loss) before taxes, excluding unallocated corporate activity 3,819 5,312   6,971 9,923
Operating Segments | Other          
Segment Reporting Information [Line Items]          
Revenues 20,672 16,640   56,246 51,314
Interest income 0 0   0 0
Interest expense 13 0   38 0
Depreciation and amortization of intangible assets 497 649   1,407 1,997
Income (loss) before taxes, excluding unallocated corporate activity 991 (261)   2,304 (971)
Unallocated corporate activity          
Segment Reporting Information [Line Items]          
Unallocated corporate activity (6,839) (10,478)   (20,931) (25,044)
Unallocated corporate activity | U.S. Regions          
Segment Reporting Information [Line Items]          
Unallocated corporate activity 0 0   0 0
Unallocated corporate activity | U.S. Federal          
Segment Reporting Information [Line Items]          
Unallocated corporate activity 0 0   0 0
Unallocated corporate activity | Canada          
Segment Reporting Information [Line Items]          
Unallocated corporate activity 0 0   0 0
Unallocated corporate activity | Small-Scale Infrastructure          
Segment Reporting Information [Line Items]          
Unallocated corporate activity 0 0   0 0
Unallocated corporate activity | Other          
Segment Reporting Information [Line Items]          
Unallocated corporate activity $ 0 $ 0   $ 0 $ 0