CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
OPERATING ACTIVITIES:
Net income	$ 22,368	$ 17,230
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	54,002	41,312
Deferred income tax	(423)	(1,138)
Amortization of debt issuance costs	3,657	784
Realized loss on sale of short-term investment	0	2,287
Loss on disposal of property and equipment	127	452
Change in fair value of contingent consideration and other	914	(1,995)
Share-based compensation	10,214	11,050
Changes in assets and liabilities, net of business acquisitions:
Accounts receivable	(8,420)	(11,303)
Inventories	(3,596)	(5,464)
Prepaid expenses and other current assets	(1,959)	(9,236)
Other non-current assets	(436)	(1,811)
Accounts payable, accrued expenses and other current liabilities	(3,405)	20,287
Deferred revenue	(91)	2,083
Other non-current liabilities	4,792	(6,785)
Net cash provided by operating activities	77,744	57,753
INVESTING ACTIVITIES:
Purchases of property and equipment	(35,387)	(22,010)
Proceeds from sale of short-term investments	0	16,951
Proceeds from note receivable	446	0
Proceeds from sale of property and equipment	205	143
Cash provided by business acquisitions	26,704
Cash used in business acquisitions		(225,744)
Net cash used in investing activities	(8,032)	(230,660)
FINANCING ACTIVITIES:
Borrowings under senior credit facility	50,000	245,000
Repayments under senior credit facility	(415,000)	(30,000)
Payment of debt issuance costs	(4,221)	0
Proceeds from the issuance of common stock, net of issuance costs	349,599	0
Net cash paid for financing liabilities from business acquisitions	(33,843)	87
Proceeds from exercised stock options	3,727	9,774
Cash taxes paid in net equity settlement	(7,240)	(6,498)
Net cash (used in) provided by financing activities	(56,978)	218,363
Effect of exchange rate changes on cash and cash equivalents	(3,898)	7,089
Net increase in cash and cash equivalents	8,836	52,545
Cash and cash equivalents at beginning of period	174,935	102,055
Cash and cash equivalents at end of period	$ 183,771	$ 154,600