Summary of Significant Accounting Policies Investments in Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2013	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 53,609		$ 58,819
Available-for-sale Securities, Gross Unrealized Gains	3	2
Available-for-sale Securities, Gross Unrealized Losses	(323)	(263)
Available-for-sale Securities, Fair Value Disclosure	53,289us-gaap_AvailableForSaleSecurities		58,558us-gaap_AvailableForSaleSecurities
US Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	53,609		58,819
Available-for-sale Securities, Gross Unrealized Gains	3		2
Available-for-sale Securities, Gross Unrealized Losses	(323)		(263)
Available-for-sale Securities, Fair Value Disclosure	$ 53,289		$ 58,558

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

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

-Publisher FASB

-Name Accounting Standards Codification

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+ References

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

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Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities.

+ References

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

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Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale securities.

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