CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
OPERATING ACTIVITIES:
Net income	$ 10,992	$ 6,394
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	27,096	19,717
Deferred income tax	(1,636)	7
Amortization of debt issuance costs	1,519	393
Loss on disposal of property and equipment	146	348
Change in fair value of contingent consideration and other	379	261
Share-based compensation	4,731	5,363
Changes in assets and liabilities, net of business acquisitions:
Accounts receivable	(18,400)	(589)
Inventories	1,297	(5,207)
Prepaid expenses and other current assets	12,163	(1,988)
Other non-current assets	339	(321)
Accounts payable, accrued expenses and other current liabilities	2,974	10,189
Other non-current liabilities	(69)	(5,685)
Net cash provided by operating activities	41,531	28,882
INVESTING ACTIVITIES:
Purchases of property and equipment	(15,387)	(9,191)
Proceeds from sale of short-term investments	0	9,976
Proceeds from note receivable	221	0
Proceeds from sale of property and equipment	148	0
Cash provided by (used in) business acquisition	5,720	(193,928)
Net cash used in investing activities	(9,298)	(193,143)
FINANCING ACTIVITIES:
Borrowings under senior credit facility	25,000	210,000
Repayments under senior credit facility	(35,000)	(20,000)
Net cash paid for financing liability from business acquisition	(7,772)	0
Proceeds from exercised stock options	3,662	1,167
Cash taxes paid in net equity settlement	(6,776)	(6,128)
Net cash (used in) provided by financing activities	(20,886)	185,039
Effect of exchange rate changes on cash and cash equivalents	3,114	1,280
Net increase in cash and cash equivalents	14,461	22,058
Cash and cash equivalents at beginning of period	174,935	102,055
Cash and cash equivalents at end of period	$ 189,396	$ 124,113