v3.8.0.1
Summary of Significant Accounting Policies - Software Costs (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Accounting Policies [Abstract]      
Capitalized software $ 7.2   $ 7.3
Capitalized software, estimated useful life 5 years    
Software amortization expense $ 0.7 $ 0.6