Summary of Significant Accounting Policies - Summary of Investments Held to Maturity (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Gain (Loss) on Investments [Line Items]
Amortized Cost	$ 15,987us-gaap_HeldToMaturitySecurities	$ 27,021us-gaap_HeldToMaturitySecurities
Gross Unrealized Gain	0	18
Gross Unrealized (Loss)	(23)	0
Fair Value	15,964	27,039
Held-to-maturity Securities, Noncurrent	4,015	10,981
Current Assets [Member]
Gain (Loss) on Investments [Line Items]
Gross Unrealized Gain	0	11
Gross Unrealized (Loss)	(7)	0
Fair Value	11,965	16,051
Non Current Assets [Member]
Gain (Loss) on Investments [Line Items]
Gross Unrealized Gain	0	7
Gross Unrealized (Loss)	(16)	0
Fair Value	$ 3,999	$ 10,988

Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

+ References

No definition available.

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- Definition

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (f)

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Fair value of investments in debt securities classified as held-to-maturity.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity, not expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

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