Income Taxes Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		$ 2,100
Deferred tax assets:
Inventory provisions and uniform capitalization	$ 1	0
Accounts receivable allowances	8	8
Non-qualified stock option and restricted stock expense	245	220
Deferred maintenance revenue	302	218
Deferred tax asset, leasing liabilities	199	290
Deferred Tax Liabilities, Leasing Arrangements	(78)	(207)
Fixed assets	7
Deferred Tax Liabilities, Property, Plant and Equipment		(26)
Loss and credit carryfowards of U.S. subsidiary	25,844	24,717
Loss carryforward of foreign subsidiary and joint venture	91	145
Deferred tax assets, excess interest expense	420	496
Other accruals and reserves	326	101
Total deferred tax assets before valuation allowance	27,436	26,195
Less valuation allowance	(26,999)	(25,406)
Total deferred tax assets	437	789
Deferred tax liabilities
Acquired intangibles	(347)	(465)
Other	0	(70)
Total deferred tax liabilities	(418)	(768)
Total net deferred tax assets	$ 19	21
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		94,000
Tax years beginning prior to January 1, 2018 [Member] | Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		85,800
Tax years beginning prior to January 1, 2018 [Member] [Member] | Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		$ 8,200