CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net income	$ 109,845	$ 119,738	$ 57,425
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation expense	54,108	50,373	53,214
Amortization of intangible assets	18,045	15,015	16,003
Amortization of debt issuance costs	1,441	1,684	1,684
Deferred income taxes	12,161	1,266	2,318
Non-cash stock compensation expense	12,462	11,315	6,769
Gain on sale of property, equipment and real estate	(1,973)	(3,321)	(1,683)
Gain on insurance proceeds	(107)	0	(1,991)
Other non-cash adjustments	3,769	613	987
Change in assets and liabilities, net of effects of acquisitions
Accounts receivable, net of allowances	846	16,078	(3,252)
Inventories	68	3,257	(32,297)
Accounts payable	52,364	(51,348)	3,477
Other assets and liabilities	(17,176)	45,355	(8,720)
Net cash provided by operating activities	245,853	210,025	93,934
Cash flows from investing activities
Purchases of businesses, net of cash acquired	(124,412)	(20,970)	(38,438)
Purchases of property, equipment and real estate	(89,392)	(55,174)	(63,278)
Proceeds from sale of property, equipment and real estate	4,880	11,432	13,445
Insurance proceeds	107	1,991	0
Proceeds from sale of business	0	7,773	0
Net cash used in investing activities	(208,817)	(54,948)	(88,271)
Cash flows from financing activities
Proceeds from revolving line of credit	110,987	854,946	995,306
Repayments of proceeds from revolving line of credit	(110,987)	(859,408)	(990,844)
Repurchases of common stock under share repurchase program	(16,446)	(2,891)	0
Payments on finance lease obligations	6,697	7,759	9,926
Secured borrowings	2,445	431	2,880
Proceeds from exercise of stock options	2,704	1,327	3,396
Repurchases of common stock related to equity award activity	(1,712)	(2,044)	(977)
Acquisition-related post-closing payments, net	(1,028)	(370)	0
Earnout payments	(628)	0	0
Payments of debt issuance costs	(901)	0	(38)
Principal payments on other notes	0	(336)	(2,627)
Net cash used in financing activities	(22,263)	(16,104)	(2,830)
Net increase in cash and cash equivalents	14,773	138,973	2,833
Cash and cash equivalents
Beginning of period	150,723	11,750	8,917
End of period	165,496	150,723	11,750
Supplemental disclosure of cash flow information
Interest paid	21,715	22,361	24,210
Cash paid for income taxes, net	32,884	31,260	22,858
Non-cash investing and financing transactions
Acquisition-related holdback payments due at a future date	8,478	1,403	375
Accrued purchases of property and equipment	$ 8,333	1,963	811
Assets acquired under capital lease obligations		$ 821	$ 2,481