Investments (Details 4) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Amortized Cost
Due in less than one year, Amortized Cost	$ 297,842
Due in one to two years, Amortized Cost	107,405
Due in three to five years, Amortized Cost	15,253
Total marketable investments	420,500us-gaap_HeldToMaturitySecurities	857,394us-gaap_HeldToMaturitySecurities
Fair Value
Due in less than one year, Fair Value	297,969
Due in one to two years, Fair Value	107,522
Due in three to five years, Fair Value	15,240
Fair Value	$ 420,731	$ 857,711

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

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Fair value of held-to-maturity debt securities maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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