Consolidated Statements of Income and Comprehensive Income (Unaudited) - USD ($)
shares in Thousands, $ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Revenues:        
New and used commercial vehicle sales $ 698,838 $ 872,106 $ 2,004,236 $ 2,590,178
Parts and service sales 336,459 360,711 1,007,063 1,051,001
Lease and rental 52,452 50,545 155,491 147,634
Finance and insurance 4,870 6,164 14,206 16,373
Other 3,422 4,550 12,347 12,728
Total revenue 1,096,041 1,294,076 3,193,343 3,817,914
Cost of products sold:        
New and used commercial vehicle sales 653,992 813,178 1,868,983 2,413,712
Parts and service sales 214,916 227,775 642,678 664,697
Lease and rental 45,817 45,115 136,618 130,242
Total cost of products sold 914,725 1,086,068 2,648,279 3,208,651
Gross profit 181,316 208,008 545,064 609,263
Selling, general and administrative expense 142,280 160,776 450,812 474,712
Depreciation and amortization expense 13,014 11,228 38,482 32,051
Gain (loss) on sale of assets 1,566 26 1,571 (581)
Operating income 27,588 36,030 57,341 101,919
Interest expense, net 3,285 3,568 11,287 10,107
Income before taxes 24,303 32,462 46,054 91,812
Provision for income taxes 9,423 12,579 17,962 35,572
Net income $ 14,880 $ 19,883 $ 28,092 $ 56,240
Earnings per common share:        
Basic (in dollars per share) $ 0.38 $ 0.49 $ 0.70 $ 1.40
Diluted (in dollars per share) $ 0.37 $ 0.48 $ 0.69 $ 1.37
Weighted average shares outstanding:        
Basic (in shares) 39,617 40,361 40,138 40,235
Diluted (in shares) 40,274 41,136 40,698 41,065
Comprehensive income $ 14,889 $ 19,883 $ 28,111 $ 56,395