Annual report pursuant to Section 13 and 15(d)

Related Parties - Additional Information (Details)

v3.10.0.1
Related Parties - Additional Information (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
SFC      
Related Party Transaction [Line Items]      
Aggregate annual rent for leased aircraft usage $ 0.3 $ 0.4 $ 0.5
Oil-Chem      
Related Party Transaction [Line Items]      
Purchase from related party 1.6 1.9 2.1
SMISC Holdings, Inc.      
Related Party Transaction [Line Items]      
Purchase from related party 0.9 0.9 0.9
SMI subsidiaries      
Related Party Transaction [Line Items]      
Vehicle sales to related party $ 0.2 $ 0.2 $ 0.2
Minimum | Mr. Marcus G. Smith | SFC      
Related Party Transaction [Line Items]      
Ownership percentage 10.00%