CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
OPERATING ACTIVITIES:
Net income	$ 32,756	$ 10,992
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	27,093	27,096
Deferred income tax	(6,843)	(1,636)
Amortization of debt issuance costs	1,357	1,519
Loss on disposal of property and equipment	367	146
Change in fair value of contingent consideration and other	194	379
Share-based compensation	4,083	4,731
Changes in assets and liabilities, net of business acquisitions:
Accounts receivable	(13,705)	(18,400)
Inventories	(12,048)	1,297
Prepaid expenses and other current assets	(12,949)	12,163
Other non-current assets	(628)	339
Accounts payable, accrued expenses and other current liabilities	5,387	2,974
Deferred revenue	(188)	0
Other non-current liabilities	4,608	(69)
Net cash provided by operating activities	29,484	41,531
INVESTING ACTIVITIES:
Purchases of property and equipment	(16,086)	(15,387)
Proceeds from note receivable	245	221
Proceeds from sale of property and equipment	35	148
Cash provided by business acquisitions	0	5,720
Net cash used in investing activities	(15,806)	(9,298)
FINANCING ACTIVITIES:
Proceeds from borrowings of long-term indebtedness	67,200	25,000
Payments on debt	(57,400)	(35,000)
Net cash paid for contingent consideration	0	(7,772)
Proceeds from exercised stock options	1,750	3,662
Cash taxes paid in net equity settlement	(6,157)	(6,776)
Net cash provided by (used in) financing activities	5,393	(20,886)
Effect of exchange rate changes on cash and cash equivalents	(884)	3,114
Net increase in cash and cash equivalents	18,187	14,461
Cash and cash equivalents at beginning of period	138,838	174,935
Cash and cash equivalents at end of period	$ 157,025	$ 189,396