Balance Sheet Components - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 735,938	$ 823,963	$ 998,532
Other comprehensive loss	254	(57)	969
Ending balance	487,263	735,938	823,963
Unrealized Gains on Cash Flow Hedges [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	66	66
Other comprehensive income (loss) before reclassifications	(66)	7,587
Amounts reclassified from AOCI	0	(7,587)
Other comprehensive loss	(66)	0
Ending balance	0	66	66
Unrealized Gains (Losses) on Available-for-Sale Investments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(132)	(75)
Other comprehensive income (loss) before reclassifications	320	(68)
Amounts reclassified from AOCI	0	11
Other comprehensive loss	320	(57)
Ending balance	188	(132)	(75)
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(66)	(9)	(978)
Other comprehensive income (loss) before reclassifications	254	7,519
Amounts reclassified from AOCI	0	(7,576)
Other comprehensive loss	254	(57)	969
Ending balance	$ 188	$ (66)	$ (9)