XML 49 R37.htm IDEA: XBRL DOCUMENT v3.8.0.1
Revenue - Narratives (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Revenue from Contract with Customer [Abstract]    
Contract revenue recognized $ 38.9 $ 25.1
Remaining performance obligation $ 489.4  
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01    
Disaggregation of Revenue    
Revenue, remaining performance obligation, Percentage 87.60%  
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01    
Disaggregation of Revenue    
Revenue, remaining performance obligation, Percentage 3.20%