Marketable Securities - Additional Information (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Fair market value of investment securities exceeds cost basis	$ 28,000
Other-than-temporary impairments recorded for securities	0
Changes in unrealized gains on available for sale securities, taxes	(208,000)	(348,000)	182,000
Estimated taxes of change in value of available-for-sale securities	83,000
Gross unrealized holding gains	130,000
Gross unrealized holding losses	$ 102,000

Available for sale securities, fair market value exceeds cost basis, by amount.

No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

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- Definition

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

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Amount before tax, after reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

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-Topic 220

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-Section 45

-Paragraph 10A

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- Definition

Amount of tax expense (benefit), after reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

+ References

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-Topic 220

-SubTopic 10

-Section 45

-Paragraph 10A

-Subparagraph (e)

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- Definition

The cumulative amount of credit losses recognized in earnings related to debt securities held for which a portion of an other than temporary impairment (OTTI) was recognized in other comprehensive income (a component of shareholders' equity).

+ References

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