Balance Sheet Components - Cash, Cash Equivalents and Short-Term and Long-Term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investment Holdings [Line Items]
Cash and cash equivalents	$ 606,166	$ 1,412,517	$ 748,476
Certificates of deposit	2,823	31,351
Publicly traded equity securities	1,717	6,163
Total short-term and long-term investments	4,540	37,514
Total cash, cash equivalents and short-term and long-term investments	610,706	1,450,031
Certificates of deposit
Investment Holdings [Line Items]
Certificates of deposit	2,823	31,351
Cash
Investment Holdings [Line Items]
Cash and cash equivalents	486,648	985,382
Money market funds
Investment Holdings [Line Items]
Cash and cash equivalents	$ 119,518	$ 427,135