Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended								6 Months Ended				12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) Segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2018 USD ($)	Dec. 31, 2015 USD ($)
Basis Of Presentation And Significant Accounting Policies [Line Items]
Business segment | Segment													2
Maturity for cash and cash equivalents													90 days
Insurance coverage													$ 250,000
Interest-bearing amounts on deposit in excess of federally	$ 11,900,000												11,900,000
Inventory reserve	1,100,000				$ 1,200,000								1,100,000	$ 1,200,000
Goodwill	8,362,000				8,362,000								8,362,000	8,362,000			$ 14,097,000
Goodwill impairment loss													0	5,735,000	$ 13,981,000
Impairment charges on long lived assets													0		0
Amortization expense related to intangible assets													383,000	494,000	983,000
Increase to retained earnings	(210,774,000)				(201,865,000)								(210,774,000)	(201,865,000)
Revenues	6,954,000	$ 6,192,000	$ 6,162,000	$ 6,313,000	7,902,000	$ 7,000,000	$ 6,409,000	$ 6,791,000					25,621,000	28,102,000	26,338,000
Allowance for doubtful accounts, receivable	177,000				107,000								177,000	107,000	172,000		236,000
Contract assets	19,000												19,000			$ 166,000
Amounts associated with service contracts accounted for under Topic 840	287,000				369,000								287,000	369,000
Unearned amount to recognize in 2018													4.9
Unearned amount to recognize in 2019	0.2												0.2
Unearned amount to recognize, thereafter	0.1												0.1
Capitalized costs to obtain a contract	282,000				117,000								$ 282,000	117,000		117,000
Product delivery period to customer													One year or less.
Medical Device Excise tax included in the cost of revenue															491,000
Advertising expense													$ 811,000	990,000	955,000
Goodwill and long-lived asset impairment														6,693,000
Impairment charges on long-lived and other assets														1,000,000
Fourth Loan Modification Agreement [Member] | Silicon Valley Bank [Member] | Scenario Forecast [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Minimum consolidated revenues									$ 14,500,000	$ 13,000,000	$ 11,600,000	$ 11,400,000
Minimum adjusted EBITDA levels									$ 2,000,000	$ 4,000,000	$ 4,000,000	$ 3,500,000
Revenue from Contract with Customer [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Allowance for doubtful accounts, receivable	6,300,000												6,300,000			8,500,000
Accounting Standards Update 2014-09 [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Increase to retained earnings	(282,000)												(282,000)			(201,973,000)
Accounting Standards Update 2014-09 [Member] | Difference between Revenue Guidance in Effect Before and After Topic 606 [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Increase to retained earnings	(211,056,000)												(211,056,000)			$ 108,000
Revenues													116,000
Amounts associated with service contracts accounted for under Topic 840	287,000												287,000
Therapy [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Goodwill																	$ 5,735,000
Goodwill impairment loss														5,735,000	13,981,000
Impairment charges on long lived assets						$ 700,000
Amortization expense related to intangible assets													129,000	222,000	$ 252,000
Therapy [Member] | ASU 2017-04 [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Fair value of goodwill	100,000				3,500,000								100,000	3,500,000
Goodwill	2,100,000				7,500,000								2,100,000	$ 7,500,000
Goodwill impairment loss	1,700,000				$ 4,000,000
Level 3 [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Fair value on nonrecurring basis	$ 0												$ 0
Minimum [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Estimated useful lives of Long-lived assets													5 years
Maximum [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Estimated useful lives of Long-lived assets													15 years