Consolidated Statements of Income and Comprehensive Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Revenue	$ 1,536,316	$ 1,315,311	$ 4,308,170	$ 3,788,406
Lease and rental	62,949	60,825	183,973	177,342
Total revenue	1,599,265	1,376,136	4,492,143	3,965,748
Cost of products sold:
Lease and rental	52,223	49,924	153,316	147,015
Total cost of products sold	1,334,497	1,127,079	3,700,953	3,246,319
Gross profit	264,768	249,057	791,190	719,429
Selling, general and administrative expense	192,482	177,405	573,644	527,729
Depreciation and amortization expense	14,033	12,794	40,552	57,395
Gain (loss) on sale of assets	70	(209)	(12)	159
Operating income	58,323	58,649	176,982	134,464
Other income	1,577	0	2,316	0
Interest expense, net	7,690	4,468	23,120	13,268
Income before taxes	52,210	54,181	156,178	121,196
Provision for income taxes	13,106	12,516	38,349	29,103
Net income	$ 39,104	$ 41,665	$ 117,829	$ 92,093
Earnings per common share:
Basic (in dollars per share)	$ 1.07	$ 1.06	$ 3.21	$ 2.33
Diluted (in dollars per share)	$ 1.05	$ 1.03	$ 3.13	$ 2.27
Weighted average shares outstanding:
Basic (in shares)	36,545	39,309	36,744	39,480
Diluted (in shares)	37,351	40,388	37,625	40,635
Dividends declared per common share (in dollars per share)	$ 0.13	$ 0.12	$ 0.37	$ 0.12
Comprehensive income	$ 39,159	$ 41,665	$ 117,763	$ 92,093
New and Used Commercial Vehicle [Member]
Revenues:
Revenue	1,070,868	878,845	2,933,952	2,508,970
Cost of products sold:
Cost of products sold	997,946	808,634	2,717,484	2,311,156
Parts and Service [Member]
Revenues:
Revenue	454,785	426,845	1,341,305	1,250,080
Cost of products sold:
Cost of products sold	284,328	268,521	830,153	788,148
Finance and Insurance [Member]
Revenues:
Revenue	5,863	5,053	18,874	15,286
Product and Service, Other [Member]
Revenues:
Revenue	$ 4,800	$ 4,568	$ 14,039	$ 14,070