Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Contract with Customer, Asset, after Allowance for Credit Loss	$ 1,300		$ 1,200
Operating Revenue	166,318	$ 139,536
Revenue from Contract with Customer, Including Assessed Tax	3,500	2,800
fuel surcharge [Member]
Disaggregation of Revenue [Line Items]
Fuel surcharge revenue	$ 19,500	$ 17,000