Balance Sheet Components - Summary of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Cash	$ 1,629	$ 1,964
Cash equivalents:
Money market accounts	123,396	107,043
Total cash and cash equivalents	$ 125,025	$ 109,007	$ 140,871	$ 150,180