CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 32,828	$ 20,717
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	50,436	39,388
Gain on bargain purchase	0	(10,796)
Loss on sales and/or abandonment of property and equipment	425	219
Write-off of patents and intangible assets	744	86
Acquired in-process research and development	382	12,136
Amortization of deferred credits	(106)	(111)
Amortization of long-term debt issuance costs	603	514
Deferred income taxes	0	(290)
Stock-based compensation expense	4,494	2,883
Changes in operating assets and liabilities, net of effects from acquisitions:
Trade receivables	(25,482)	(10,963)
Other receivables	255	(449)
Inventories	(19,375)	(9,922)
Prepaid expenses and other current assets	(2,719)	(1,587)
Prepaid income taxes	(120)	(231)
Income tax refund receivables	134	280
Other assets	(1,370)	(2,992)
Trade payables	15,936	(876)
Accrued expenses	7,707	4,470
Income taxes payable	(1,528)	(764)
Deferred compensation payable	994	1,107
Other long-term obligations	(1,381)	574
Total adjustments	30,029	22,676
Net cash provided by operating activities	62,857	43,393
Capital expenditures for:
Property and equipment	(47,024)	(29,522)
Intangible assets	(2,234)	(1,927)
Proceeds from the sale of property and equipment	7	9
Issuance of note receivable	(10,750)	0
Cash paid in acquisitions, net of cash acquired	(122,770)	(103,500)
Net cash used in investing activities	(182,771)	(134,940)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock	213,276	143,069
Offering costs	(366)	(816)
Proceeds from issuance of long-term debt	380,825	151,462
Payments on long-term debt	(450,575)	(197,962)
Contingent payments related to acquisitions	(184)	(45)
Payment of taxes related to an exchange of common stock	(2,616)	0
Net cash provided by financing activities	140,360	95,708
EFFECT OF EXCHANGE RATES ON CASH	(827)	30
NET INCREASE IN CASH AND CASH EQUIVALENTS	19,619	4,191
CASH AND CASH EQUIVALENTS:
Beginning of period	32,336	19,171
End of period	51,955	23,362
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Interest (net of capitalized interest of $468 and $371, respectively)	8,018	5,953
Income taxes	6,069	4,029
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Property and equipment purchases in accounts payable	3,058	1,394
Acquisition purchases in accrued expenses and other long-term obligations	0	12,000
Merit common stock surrendered (43 and 0 shares, respectively) in exchange for exercise of stock options	$ 2,262	$ 0