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)

v3.6.0.2
Composition of Certain Financial Statement Captions - Summary of available-for-sale securities' fair value and gross unrealized losses (Details) - USD ($)
$ in Thousands
Dec. 31, 2016
Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, continuous unrealized loss position, twelve months or less, fair value $ 34,257 $ 81,045
Available-for-sale securities, continuous unrealized loss position, twelve months or less, gross unrealized losses (52) (295)
Available-for-sale securities, continuous unrealized loss position, more than twelve months, fair value 4,099 8,531
Available-for-sale securities, continuous unrealized loss position, more than twelve months, gross unrealized losses (3) (54)
Available-for-sale securities, continuous unrealized loss position, total, fair value 38,356 89,576
Available-for-sale securities, continuous unrealized loss position, total, gross unrealized losses (55) (349)
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 64,804
Available-for-sale securities, continuous unrealized loss position, twelve months or less, gross unrealized losses (52) (293)
Available-for-sale securities, continuous unrealized loss position, more than twelve months, fair value 4,099 8,531
Available-for-sale securities, continuous unrealized loss position, more than twelve months, gross unrealized losses (3) (54)
Available-for-sale securities, continuous unrealized loss position, total, fair value 38,356 73,335
Available-for-sale securities, continuous unrealized loss position, total, gross unrealized losses $ (55) (347)
U.S. government and government agency debt securities    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, continuous unrealized loss position, twelve months or less, fair value   16,241
Available-for-sale securities, continuous unrealized loss position, twelve months or less, gross unrealized losses   (2)
Available-for-sale securities, continuous unrealized loss position, more than twelve months, fair value   0
Available-for-sale securities, continuous unrealized loss position, more than twelve months, gross unrealized losses   0
Available-for-sale securities, continuous unrealized loss position, total, fair value   16,241
Available-for-sale securities, continuous unrealized loss position, total, gross unrealized losses   $ (2)