v3.8.0.1
Summary of Significant Accounting Policies - Reserves for Self-Insurance Benefits (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Accounting Policies [Abstract]    
Stop-loss amount $ 0.3  
Self-insurance reserves 1.1 $ 1.7
Workers compensation reserve $ 1.7 $ 1.3