Annual report pursuant to Section 13 and 15(d)

Composition of Certain Financial Statement Captions - Summary of available-for-sale securities' fair value and gross unrealized losses (Details)

v3.8.0.1
Composition of Certain Financial Statement Captions - Summary of available-for-sale securities' fair value and gross unrealized losses (Details)
$ in Thousands
Dec. 31, 2016
USD ($)
Schedule of Available-for-sale Securities [Line Items]  
Available-for-sale securities, continuous unrealized loss position, twelve months or less, fair value $ 34,257
Available-for-sale securities, continuous unrealized loss position, twelve months or less, gross unrealized losses (52)
Available-for-sale securities, continuous unrealized loss position, more than twelve months, fair value 4,099
Available-for-sale securities, continuous unrealized loss position, more than twelve months, gross unrealized losses (3)
Available-for-sale securities, continuous unrealized loss position, total, fair value 38,356
Available-for-sale securities, continuous unrealized loss position, total, gross unrealized losses (55)
Corporate debt securities  
Schedule of Available-for-sale Securities [Line Items]  
Available-for-sale securities, continuous unrealized loss position, twelve months or less, fair value 34,257
Available-for-sale securities, continuous unrealized loss position, twelve months or less, gross unrealized losses (52)
Available-for-sale securities, continuous unrealized loss position, more than twelve months, fair value 4,099
Available-for-sale securities, continuous unrealized loss position, more than twelve months, gross unrealized losses (3)
Available-for-sale securities, continuous unrealized loss position, total, fair value 38,356
Available-for-sale securities, continuous unrealized loss position, total, gross unrealized losses $ (55)