CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income	$ 118,763	$ 97,239	$ 68,159
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization of property and equipment	43,562	41,339	38,862
Amortization of operating lease right-of-use assets	22,258	18,122	15,691
Amortization of intangibles	37,079	28,535	24,510
Amortization of deferred financing costs and debt discount	1,354	1,332	1,184
Provision for credit losses	2,227	4,444	4,312
Write-off of debt issuance costs	1,767	0	3,725
Gain on sale of property and equipment	(1,840)	(786)	(140)
Noncash stock compensation	13,752	10,826	8,727
Deferred income taxes	(438)	(8,475)	5,341
Amortization of terminated interest rate swap	3,223	1,326	0
Changes in assets and liabilities, excluding effects of acquisitions
Accounts receivable	(16,775)	(10,489)	(29,582)
Inventories	(54,003)	187	(10,597)
Other assets	(19,885)	(870)	(16,959)
Accounts payable	26,424	(203)	947
Income taxes receivable/payable	(4,403)	4,296	(3,944)
Other liabilities	(34,751)	(6,034)	12,831
Net cash provided by operating activities	138,314	180,789	123,067
Cash flows from investing activities
Purchases of investments	0	(776)	(52,795)
Maturities of short term investments	0	38,693	25,061
Purchases of property and equipment	(36,979)	(33,587)	(50,167)
Acquisitions of businesses, net of cash acquired of $1,707, $0 and $334 in 2021, 2020 and 2019, respectively	(241,308)	(76,446)	(51,706)
Proceeds from sale of property and equipment	2,694	1,187	761
Other	(2,846)	(6,865)	(2,887)
Net cash used in investing activities	(278,439)	(77,794)	(131,733)
Cash flows from financing activities
Proceeds from senior notes (Note 8)	0	0	300,000
Proceeds from term loan (Note 8)	500,000	0	0
Payments on term loan (Note 8)	(200,000)	0	(195,750)
Proceeds from vehicle and equipment notes payable	27,834	21,290	33,090
Debt issuance costs	(7,520)	(157)	(6,691)
Principal payments on long-term debt	(26,301)	(26,685)	(21,316)
Principal payments on finance lease obligations	(2,125)	(2,632)	(4,157)
Acquisition-related obligations	(8,918)	(6,283)	(6,732)
Dividends paid	(35,294)	0	0
Repurchase of common stock	0	(33,924)	0
Surrender of common stock awards by employees	(5,586)	(973)	(2,331)
Net cash provided by (used in) financing activities	242,090	(49,364)	96,113
Net change in cash and cash equivalents	101,965	53,631	87,447
Cash and cash equivalents at beginning of period	231,520	177,889	90,442
Cash and cash equivalents at end of period	333,485	231,520	177,889
Supplemental disclosures of cash flow information
Interest	25,976	26,324	20,943
Income taxes, net of refunds	39,241	37,072	22,633
Supplemental disclosure of noncash activities
Right-of-use assets obtained in exchange for operating lease obligations	38,084	26,001	18,907
Release of indemnification of acquisition-related debt	2,036	0	0
Termination of operating lease obligations and right-of-use assets	0	0	(2,946)
Property and equipment obtained in exchange for finance lease obligations	2,735	1,000	2,809
Seller obligations in connection with acquisition of businesses	29,169	14,086	7,543
Unpaid purchases of property and equipment included in accounts payable	$ 441	$ 1,013	$ 1,903