Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
As reported on the consolidated balance sheets:
Current marketable investments	$ 297,842us-gaap_HeldToMaturitySecuritiesCurrent	$ 409,645us-gaap_HeldToMaturitySecuritiesCurrent
Noncurrent marketable investments	122,658	447,749
Total marketable investments	$ 420,500us-gaap_HeldToMaturitySecurities	$ 857,394us-gaap_HeldToMaturitySecurities

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

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