CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 27,523	$ 20,121	$ 23,802
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	53,582	43,755	37,425
Gain on bargain purchase	(11,039)	0	0
Losses (gains) on sales and/or abandonment of property and equipment	427	530	(23)
Write-off of patents and intangible assets	988	101	141
Acquired in-process research and development	12,136	461	1,000
Amortization of deferred credits	(147)	(170)	(171)
Amortization of long-term debt issuance costs	685	952	987
Deferred income taxes	(1,304)	(962)	3,450
Excess tax benefits from stock-based compensation	0	(669)	(2,124)
Stock-based compensation expense	4,075	2,506	2,243
Changes in operating assets and liabilities, net of effects from acquisitions:
Trade receivables	(12,844)	(6,816)	(5,872)
Other receivables	(3,557)	1,161	335
Inventories	(17,834)	(3,656)	(13,113)
Prepaid expenses and other current assets	(1,236)	271	(696)
Prepaid income taxes	(611)	404	(1,788)
Income tax refund receivables	(588)	406	(784)
Other assets	(3,735)	(3,763)	(362)
Trade payables	417	(6,835)	14,766
Accrued expenses	6,461	3,242	5,873
Income taxes payable	21	1,451	2,199
Long-term income taxes payable	4,846	0	0
Liabilities related to unrecognized tax benefits	(19)	597	536
Deferred compensation payable	1,970	712	(135)
Other long-term obligations	2,510	(200)	1,769
Total adjustments	35,204	33,478	45,656
Net cash provided by operating activities	62,727	53,599	69,458
Capital expenditures for:
Property and equipment	(38,623)	(32,837)	(50,959)
Intangible assets	(2,577)	(2,217)	(1,956)
Proceeds from sale-leaseback transactions	0	0	2,017
Proceeds from sale of cost method investment	0	1,089	0
Proceeds from the sale of property and equipment	21	19	1,247
Cash paid in acquisitions, net of cash acquired	(105,582)	(125,161)	(12,368)
Net cash used in investing activities	(146,761)	(159,107)	(62,019)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock	143,810	5,271	6,668
Offering costs	(816)	0	0
Proceeds from issuance of long-term debt	197,214	219,505	152,375
Payments on long-term debt	(243,214)	(102,098)	(169,272)
Excess tax benefits from stock-based compensation	0	669	2,124
Long-term debt issuance costs	(416)	(1,948)	0
Contingent payments related to acquisitions	(61)	(218)	(1,212)
Payment of taxes related to an exchange of common stock	0	(86)	(918)
Net cash provided by (used in) financing activities	96,517	121,095	(10,235)
EFFECT OF EXCHANGE RATES ON CASH	682	(593)	(382)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	13,165	14,994	(3,178)
CASH AND CASH EQUIVALENTS:
Beginning of year	19,171	4,177	7,355
End of year	32,336	19,171	4,177
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Interest (net of capitalized interest of $513, $460 and $325, respectively)	7,707	8,872	6,273
Income taxes	6,049	2,318	3,409
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES
Property and equipment purchases in accounts payable	1,992	2,398	3,199
Cost method investment converted to intangible asset in acquisition in lieu of additional cash payment	0	0	1,010
Contingent receivable in exchange for sale of cost method investment	0	711	0
Receivable for issuance of common stock associated with option exercises	137	0	0
Acquisition purchases in accrued expenses and other long-term obligations	10,488	0	1,300
Merit common stock surrendered (0, 14 and 185 shares, respectively) in exchange for exercise of stock options	$ 0	$ 346	$ 3,802