Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 1,859	$ 1,841
Accumulated depreciation, Property, plant and equipment	19,016	18,436
Accumulated depreciation, Rental assets	11,248	10,879
Accumulated amortization, Intangible assets	$ 24,003	$ 22,070
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	78,699,005	73,979,882
Common stock, shares outstanding	78,699,005	73,979,882