XML 63 R41.htm IDEA: XBRL DOCUMENT v3.8.0.1
Description of Business and Summary of Significant Accounting Policies - Commissions (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Accounting Policies [Abstract]      
Commission expense $ 14.0 $ 10.2 $ 7.2