Marketable Securities - Available-for-sale Securities by Major Security Type (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Marketable Securities
Amortized cost	$ 4,521	$ 4,760
Gross unrealized holding gains	26	1
Gross unrealized holding losses	(4)	(46)
Estimated fair value	4,543	4,715
Corporate bonds and notes
Marketable Securities
Amortized cost	1,814	2,911
Gross unrealized holding gains	21	1
Gross unrealized holding losses	(3)	(31)
Estimated fair value	1,832	2,881
Municipal bonds
Marketable Securities
Amortized cost	2,707	1,849
Gross unrealized holding gains	5
Gross unrealized holding losses	(1)	(15)
Estimated fair value	$ 2,711	$ 1,834

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

No definition available.

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

No definition available.

+ Details

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- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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