v3.19.1
Segment Reporting - Interests (Details)
$ in Millions
12 Months Ended
Dec. 31, 2018
USD ($)
item
Dec. 31, 2017
USD ($)
item
Interests    
Number of major interests | item 2 2
Revenue $ 653.2 $ 675.0
Major Interest One    
Interests    
Revenue $ 97.5 $ 90.2
Percentage of revenue (as a percent) 14.90% 13.40%
Major Interest Two    
Interests    
Revenue $ 70.5 $ 105.2
Percentage of revenue (as a percent) 10.80% 15.60%