Consolidated Statements of Operations (Unaudited) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Income Statement [Abstract]        
Revenue $ 443,829,924 $ 371,642,242 $ 849,107,456 $ 655,133,816
Costs and expenses:        
Transportation costs 358,652,347 302,100,945 683,103,064 532,340,803
Selling, general and administrative expenses 70,532,891 61,450,284 140,009,379 105,478,097
Depreciation and amortization 7,598,376 5,251,020 15,127,709 9,124,157
Income from operations 7,046,310 2,839,993 10,867,304 8,190,759
Interest income 0 23,909 0 23,909
Interest expense (3,524,166) (4,350,256) (7,027,561) (4,388,224)
Other expense 0 (74,274) 0 (126,295)
Interest and other expense (3,524,166) (4,400,621) (7,027,561) (4,490,610)
Income (Loss) before provision for income taxes 3,522,144 (1,560,628) 3,839,743 3,700,149
Income tax (expense) benefit (1,591,375) 879,000 (1,646,363) (1,054,000)
Net income (loss) $ 1,930,769 $ (681,628) $ 2,193,380 $ 2,646,149
Earnings (Loss) per common share:        
Basic (in usd per share) $ 0.07 $ (0.03) $ 0.08 $ 0.10
Diluted (in usd per share) $ 0.07 $ (0.03) $ 0.07 $ 0.10