Annual report pursuant to Section 13 and 15(d)

Lease Obligations - Narrative (Details)

v3.8.0.1
Lease Obligations - Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Leases [Abstract]      
Maximum lease expiration year 2023    
Rent expense $ 0.3 $ 0.3 $ 0.4