Balance Sheet Components - Deferred Revenue (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Deferred Revenue Arrangement [Line Items]
Deferred revenue	$ 673,892	$ 618,622
Subscription Arrangement
Deferred Revenue Arrangement [Line Items]
Deferred revenue	55,300
Annual Membership Fees
Deferred Revenue Arrangement [Line Items]
Deferred revenue	$ 673,900