Balance Sheet Components - Intangible Assets, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 31,856	$ 31,856
Accumulated Amortization	31,189	28,521
Net Carrying Amount	667	3,335
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,293	2,293
Accumulated Amortization	2,293	2,293
Net Carrying Amount	0	0
User relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	18,678	18,678
Accumulated Amortization	18,011	15,343
Net Carrying Amount	667	3,335
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	10,356	10,356
Accumulated Amortization	10,356	10,356
Net Carrying Amount	0	0
Domain names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	529	529
Accumulated Amortization	529	529
Net Carrying Amount	$ 0	$ 0