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Marketable Securities - Available-for-sale Securities by Major Security Type (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Marketable Securities [Line Items]
Amortized cost	$ 2,751	$ 2,848
Gross unrealized holding gains	23	31
Gross unrealized holding losses
Estimated fair value	2,774	2,879
Corporate bonds and notes [Member]
Marketable Securities [Line Items]
Amortized cost	1,008	1,312
Gross unrealized holding gains	20	26
Gross unrealized holding losses
Estimated fair value	1,028	1,338
Municipal bonds [Member]
Marketable Securities [Line Items]
Amortized cost	1,743	1,536
Gross unrealized holding gains	3	5
Gross unrealized holding losses
Estimated fair value	$ 1,746	$ 1,541

X

- Definition

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

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	debit
Period Type:	instant

X

- 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=121645371&loc=d3e27161-111563

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X

- 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.

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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

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X

- 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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