Annual report pursuant to Section 13 and 15(d)

Operating Leases - Narrative (Details)

v3.8.0.1
Operating Leases - Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Leases [Abstract]      
Rent expense $ 12.3 $ 10.4 $ 5.8