Composition of Certain Financial Statement Items (Property and Equipment) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Less: accumulated depreciation and amortization	$ (50,145)	$ (49,184)
Property and equipment, net	28,747	28,281
Equipment held for rental or loan
Property, Plant and Equipment [Line Items]
Property and equipment, gross	42,746	42,949
Manufacturing equipment and computers
Property, Plant and Equipment [Line Items]
Property and equipment, gross	26,290	24,827
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,827	5,697
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,483	2,446
Building and improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,276	1,276
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 270	$ 270