Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities
Net income	$ 44,315	$ 40,045	$ 43,209
Adjustments to reconcile net income to cash provided by operating activities:
Provision for doubtful accounts	187	482	965
Depreciation - PP&E	11,616	11,267	11,381
Depreciation - Rental	5,531	6,429	7,607
Amortization of intangibles	3,317	3,104	3,113
Amortization of debt issuance	203	213	214
Stock-based compensation expense	1,869	1,414	1,057
Provision for deferred income tax expense	1,328	2,620	2,804
Gain on sale of property, plant and equipment	(341)	(345)	(4,046)
Changes in operating assets and liabilities, net of effect of acquisitions:
Accounts receivable	(23,134)	3,876	(9,657)
Inventories	142	12,340	9,759
Rental equipment	(3,054)	315	(11,699)
Prepaid expenses and other	2,845	(5,634)	(3,521)
Trade accounts payable and accrued liabilities	11,688	(5,382)	(1,708)
Income taxes payable	2,357	2,908	3,700
Long term tax payable	12,478	0	0
Other assets and liabilities, net	(543)	2,132	(760)
Net cash provided by operating activities	70,804	75,784	52,418
Investing Activities
Acquisitions, net of cash acquired	(38,553)	(188)	(3,465)
Purchase of property, plant and equipment	(13,490)	(9,711)	(15,479)
Proceeds from sale of property, plant and equipment	767	1,293	4,246
Purchase of patents	0	(50)	0
Net cash used in investing activities	(51,276)	(8,656)	(14,698)
Financing Activities
Borrowings on bank revolving credit facility	143,000	79,000	79,000
Repayment on bank revolving credit facility	(153,000)	(153,000)	(125,000)
Principal payments on long-term debt and capital leases	(17)	(38)	(449)
Proceeds from issuance of long-term debt	0	48	0
Debt issuance cost	0	(593)	0
Dividends paid	(4,614)	(4,114)	(3,628)
Proceeds from exercise of stock options	2,397	1,369	2,023
Common stock repurchased	(166)	(19)	0
Net cash used in financing activities	(12,400)	(77,347)	(48,054)
Effect of exchange rate changes on cash	1,452	90	(2,277)
Net change in cash and cash equivalents	8,580	(10,129)	(12,611)
Cash and cash equivalents at beginning of the year	16,793	26,922	39,533
Cash and cash equivalents at end of the year	25,373	16,793	26,922
Cash paid during the year for:
Interest	5,217	5,796	6,936
Income taxes	$ 23,175	$ 16,637	$ 18,709