Quarterly report pursuant to Section 13 or 15(d)

Marketable Securities - Continuous Unrealized Loss Position (Details)

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Marketable Securities - Continuous Unrealized Loss Position (Details)
$ in Thousands
Mar. 31, 2017
USD ($)
Investments in an Unrealized Loss Position  
Fair Value $ 1,264,172
Gross Unrealized Losses, less than 12 months (5,203) [1]
Corporate debt securities  
Investments in an Unrealized Loss Position  
Fair Value 705,236
Gross Unrealized Losses, less than 12 months (2,299) [1]
U.S. Government agency securities  
Investments in an Unrealized Loss Position  
Fair Value 287,570
Gross Unrealized Losses, less than 12 months (1,670) [1]
U.S. Treasury securities  
Investments in an Unrealized Loss Position  
Fair Value 217,914
Gross Unrealized Losses, less than 12 months (1,164) [1]
Sovereign securities  
Investments in an Unrealized Loss Position  
Fair Value 53,452
Gross Unrealized Losses, less than 12 months $ (70) [1]
[1] As of March 31, 2017, the amount of total gross unrealized losses related to investments that had been in a continuous loss position for 12 months or more was immaterial.