Marketable Securities - Schedule of Available-for-sale Securities (Details) $ in Thousands	Sep. 30, 2017 USD ($)
Less than 12 Months - Estimated Fair Value	$ 7,445
Less than 12 Months - Gross Unrealized Holding Losses	(29)
More than 12 Months - Estimated Fair Value	2,714
More than 12 Months - Gross Unrealized Holding Losses	(31)
Total Estimated Fair Value	10,159
Total Gross Unrealized Holding Losses	(60)
Corporate Bonds and Notes [Member]
Less than 12 Months - Estimated Fair Value	4,288
Less than 12 Months - Gross Unrealized Holding Losses	(24)
More than 12 Months - Estimated Fair Value	2,148
More than 12 Months - Gross Unrealized Holding Losses	(27)
Total Estimated Fair Value	6,436
Total Gross Unrealized Holding Losses	(51)
Municipal Bonds [Member]
Less than 12 Months - Estimated Fair Value	3,157
Less than 12 Months - Gross Unrealized Holding Losses	(5)
More than 12 Months - Estimated Fair Value	566
More than 12 Months - Gross Unrealized Holding Losses	(4)
Total Estimated Fair Value	3,723
Total Gross Unrealized Holding Losses	$ (9)

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

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