Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Contingent Consideration (Details)

v3.8.0.1
Fair Value Measurements - Contingent Consideration (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Recurring      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value $ 414 $ 541  
Recurring | Level 1      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value 0 0  
Recurring | Level 2      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value 0 0  
Recurring | Level 3      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value 414 541  
Contingent Consideration      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value 414 541 $ 841
Contingent Consideration | Recurring | AssetEye      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value 247 539  
Contingent Consideration | Recurring | Axiometrics      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value 167    
Contingent Consideration | Recurring | Indatus      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value   2  
Contingent Consideration | Recurring | Level 1 | AssetEye      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value 0 0  
Contingent Consideration | Recurring | Level 1 | Axiometrics      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value 0    
Contingent Consideration | Recurring | Level 1 | Indatus      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value   0  
Contingent Consideration | Recurring | Level 2 | AssetEye      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value 0 0  
Contingent Consideration | Recurring | Level 2 | Axiometrics      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value 0    
Contingent Consideration | Recurring | Level 2 | Indatus      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value   0  
Contingent Consideration | Recurring | Level 3 | AssetEye      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value 247 539  
Contingent Consideration | Recurring | Level 3 | Axiometrics      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value 167    
Contingent Consideration | Recurring | Level 3 | Indatus      
Business Acquisition, Contingent Consideration [Line Items]      
Liability measured at fair value   2  
Interest rate swap agreements | Recurring      
Business Acquisition, Contingent Consideration [Line Items]      
Interest rate swap agreements 1,329 1,098  
Interest rate swap agreements | Recurring | Level 1      
Business Acquisition, Contingent Consideration [Line Items]      
Interest rate swap agreements 0 0  
Interest rate swap agreements | Recurring | Level 2      
Business Acquisition, Contingent Consideration [Line Items]      
Interest rate swap agreements 1,329 1,098  
Interest rate swap agreements | Recurring | Level 3      
Business Acquisition, Contingent Consideration [Line Items]      
Interest rate swap agreements $ 0 $ 0