Annual report pursuant to Section 13 and 15(d)

Related Party Transactions - Additional Information (Details)

v3.10.0.1
Related Party Transactions - Additional Information (Details) - Old Dominion Truck Leasing Inc [Member] - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Related Party Transaction [Line Items]    
Rental service charge $ 6,000 $ 12,000
Purchase of maintenance and other services $ 110,000 $ 254,000