Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues
Revenue	$ 4,499,717	$ 5,562,298	$ 5,267,952
Lease and rental	236,223	247,549	238,238
Total revenue	4,735,940	5,809,847	5,506,190
Cost of products sold
Lease and rental	202,412	206,200	197,271
Total cost of products sold	3,860,473	4,784,219	4,527,921
Gross profit	875,467	1,025,628	978,269
Selling, general and administrative	665,258	753,749	705,226
Depreciation and amortization	57,456	55,372	70,489
Gain (loss) on sale of assets	1,852	(102)	297
Operating income	154,605	216,405	202,851
Other income	6,132	1,925	0
Interest income (expense):
Interest income	713	1,680	1,376
Interest expense	(9,727)	(30,487)	(21,058)
Total interest expense, net	9,014	28,807	19,682
Income before taxes	151,723	189,523	183,169
Income tax provision	36,836	47,940	44,107
Net income	$ 114,887	$ 141,583	$ 139,062
Earnings per common share
Basic (in dollars per share)	$ 2.09	$ 2.57	$ 2.36
Diluted (in dollars per share)	2.04	2.51	2.30
Dividends declared per common share (in dollars per share)	$ 0.41	$ 0.34	$ 0.16
New and Used Commercial Vehicle [Member]
Revenues
Revenue	$ 2,863,309	$ 3,757,584	$ 3,558,637
Cost of products sold
Cost of products sold	2,641,487	3,480,682	3,280,966
Parts and Service [Member]
Revenues
Revenue	1,600,445	1,762,510	1,670,052
Cost of products sold
Cost of products sold	1,016,574	1,097,337	1,049,684
Finance and Insurance [Member]
Revenues
Revenue	21,949	24,443	20,535
Product and Service, Other [Member]
Revenues
Revenue	$ 14,014	$ 17,761	$ 18,728