Summary Of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Significant Accounting Policies [Line Items]
Number of reportable segments | segment	2
Term of securities classified as current, expected to be used in operations, sold or transferred	12 months
Investment income	$ 996,000	$ 332,000
Allowance for doubtful accounts	325,000	807,000
Goodwill impairment	1,257,000	0	$ 0
Depreciation expense	2,554,000	1,909,000	1,679,000
Amortization expense of intangible assets	77,000	155,000	180,000
Impairment of long-lived assets from continuing operations	0
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	0	0
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0
Other assets, net	6,055,000	3,427,000
Amortization expense	456,000	739,000	455,000
Tax related interest accrued		0	0
Income Tax Examination, Penalties and Interest Accrued	0	$ 0
Maximum term		6 years
Advertising costs	2,650,000	$ 3,419,000	1,696,000
Research and development	3,830,000	4,671,000	4,458,000
Self-Fitting Software [Member]
Significant Accounting Policies [Line Items]
Other assets, net	3,679,000
Technology Access [Member]
Significant Accounting Policies [Line Items]
Other assets, net	$ 1,866,000	2,259,000
Minimum [Member]
Significant Accounting Policies [Line Items]
Acquired finite-lived intangible assets amortization period	18 years
Minimum [Member] | Building and Improvements [Member]
Significant Accounting Policies [Line Items]
Estimated useful life	5 years
Minimum [Member] | Machinery and Equipment [Member]
Significant Accounting Policies [Line Items]
Estimated useful life	3 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Acquired finite-lived intangible assets amortization period	20 years
Maximum [Member] | Building and Improvements [Member]
Significant Accounting Policies [Line Items]
Estimated useful life	40 years
Maximum [Member] | Machinery and Equipment [Member]
Significant Accounting Policies [Line Items]
Estimated useful life	12 years
Hearing Help Express (HHE) [Member]
Significant Accounting Policies [Line Items]
Impairment of Intangible Assets, Finite-lived	$ 2,508,000
Customer Funded Tooling [Member]
Significant Accounting Policies [Line Items]
Research and development	$ 25,000	$ (184,000)	$ 95,000
Stock Options [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Vesting period	3 years
Stock Options [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Vesting period	10 years
Maximum term	10 years
Restricted Stock Units (RSUs) [Member]
Significant Accounting Policies [Line Items]
Vesting period	3 years