Balance Sheet Components - Available-for-Sale Investments in Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 15,497	$ 29,195
Unrealized Loss, Less than 12 months	(3)	(7)
Corporate bonds/notes
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	5,369	10,128
Unrealized Loss, Less than 12 months	(1)	(4)
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	10,128	19,067
Unrealized Loss, Less than 12 months	$ (2)	$ (3)