Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Details)

v3.10.0.1
Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Details) - USD ($)
$ in Thousands
Jun. 30, 2018
Dec. 31, 2017
Jun. 30, 2017
Dec. 31, 2016
Contingent Consideration | Level 3        
Business Acquisition, Contingent Consideration [Line Items]        
Liabilities measured at fair value $ 52 $ 414 $ 1,394 $ 541
Recurring        
Business Acquisition, Contingent Consideration [Line Items]        
Liabilities measured at fair value 52 414    
Recurring | Level 1        
Business Acquisition, Contingent Consideration [Line Items]        
Liabilities measured at fair value 0 0    
Recurring | Level 2        
Business Acquisition, Contingent Consideration [Line Items]        
Liabilities measured at fair value 0 0    
Recurring | Level 3        
Business Acquisition, Contingent Consideration [Line Items]        
Liabilities measured at fair value 52 414    
Recurring | Contingent Consideration | AssetEye        
Business Acquisition, Contingent Consideration [Line Items]        
Liabilities measured at fair value   247    
Recurring | Contingent Consideration | AssetEye | Level 1        
Business Acquisition, Contingent Consideration [Line Items]        
Liabilities measured at fair value   0    
Recurring | Contingent Consideration | AssetEye | Level 2        
Business Acquisition, Contingent Consideration [Line Items]        
Liabilities measured at fair value   0    
Recurring | Contingent Consideration | AssetEye | Level 3        
Business Acquisition, Contingent Consideration [Line Items]        
Liabilities measured at fair value   247    
Recurring | Contingent Consideration | Axiometrics        
Business Acquisition, Contingent Consideration [Line Items]        
Liabilities measured at fair value 52 167    
Recurring | Contingent Consideration | Axiometrics | Level 1        
Business Acquisition, Contingent Consideration [Line Items]        
Liabilities measured at fair value 0 0    
Recurring | Contingent Consideration | Axiometrics | Level 2        
Business Acquisition, Contingent Consideration [Line Items]        
Liabilities measured at fair value 0 0    
Recurring | Contingent Consideration | Axiometrics | Level 3        
Business Acquisition, Contingent Consideration [Line Items]        
Liabilities measured at fair value 52 167    
Recurring | Interest rate swap agreements        
Business Acquisition, Contingent Consideration [Line Items]        
Assets measured at fair value 1,465 1,329    
Recurring | Interest rate swap agreements | Level 1        
Business Acquisition, Contingent Consideration [Line Items]        
Assets measured at fair value 0 0    
Recurring | Interest rate swap agreements | Level 2        
Business Acquisition, Contingent Consideration [Line Items]        
Assets measured at fair value 1,465 1,329    
Recurring | Interest rate swap agreements | Level 3        
Business Acquisition, Contingent Consideration [Line Items]        
Assets measured at fair value $ 0 $ 0