Annual report pursuant to Section 13 and 15(d)

Composition of Certain Financial Statement Captions - Schedule of available-for-sale investments by contractual maturity date (Details)

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Composition of Certain Financial Statement Captions - Schedule of available-for-sale investments by contractual maturity date (Details) - USD ($)
$ in Thousands
Dec. 31, 2016
Dec. 31, 2015
Adjusted Cost    
Due in one year or less $ 92,914 $ 266,205
Due after one year through three years 6,251 46,655
Total 99,165 312,860
Fair Value    
Due in one year or less 92,861 266,150
Due after one year through three years 6,252 46,369
Total $ 99,113 $ 312,519